Hypogonadotropic Hypogonadism in Morbidly Obese Males Is Reversed After Bariatric Surgery

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1 DOI /s CLINICAL RESEARCH Hypogonadotropic Hypogonadism in Morbidly Obese Males Is Reversed After Bariatric Surgery Silvia Pellitero & Izaskun Olaizola & Antoni Alastrue & Eva Martínez & María Luisa Granada & Jose María Balibrea & Pau Moreno & Assumpta Serra & Maruja Navarro-Díaz & Ramon Romero & Manel Puig-Domingo # Springer Science + Business Media, LLC 2012 Abstract Background The effect of weight loss by bariatric surgery on gonadal hormones in morbidly obese males is not entirely known. The main objective of the study was to analyze gonadal hormonal changes after weight loss. Methods An observational study was conducted before and after 12 months of weight loss at a clinical research center. Thirty-three men [age 40.5±9.9, body mass index (BMI) 50.3±6.1 kg/m 2 ] undergoing bariatric surgery were included. The main outcome measures were as follows: changes in total (TT) and free testosterone (FT), estradiol (E2), sex hormone binding globulin (SHBG), luteinizing hormone (LH), folliclestimulating hormone (FSH), anti-müllerian hormone (AMH), inhibin B, and prolactin (PRL). Results Baseline prevalence of hypogonadism (defined by TT<300 ng/dl or FT<65 pg/ml) was 78.8 and 51.5 %, S. Pellitero (*) : I. Olaizola : E. Martínez : M. Puig-Domingo Endocrinology and Nutrition Service, Department of Internal Medicine, Universitat Autònoma de Barcelona, Germans Trias i Pujol University Hospital, Via Canyet, Badalona, Barcelona, Spain spellitero.germanstrias@gencat.cat M. L. Granada Clinical Biochemistry Service, Universitat Autònoma de Barcelona, Germans Trias i Pujol University Hospital, Via Canyet, Badalona, Barcelona, Spain A. Alastrue : J. M. Balibrea : P. Moreno Surgery Department, Universitat Autònoma de Barcelona, Germans Trias i Pujol Hospital, Badalona, Barcelona, Spain A. Serra : M. Navarro-Díaz : R. Romero Nephrology Service, Department of Internal Medicine, Universitat Autònoma de Barcelona, Germans Trias i Pujol University Hospital, Via Canyet, Badalona, Barcelona, Spain respectively. Hypogonadal patients were older and showed inhibin B and AMH significantly lower than those with normal TT. BMI correlated negatively with TT, LH, and SHBG. Regression analyses showed a significant and independent association of hypogonadism with age (OR01.2, p00.01), BMI (OR01.3, p00.03), and AMH (OR00.4, p0 0.03) after adjustments. After 1 year, percentage of weight loss (%WL) was 18.8±5.2 %, and there was a significant increase of TT, FT, SHBG, and FSH and a decrease of E2 and PRL. Prevalence of persistent hypogonadism after surgery was 6 % (low TT) and 15 % (low FT). %WL was significantly associated with percent changes in SHBG (r0 0.4, p00.04), inhibin B (r0 0.4, p00.03), and AMH (r0 0.4, p00.01). Age and %WL were the only significant and independent parameters associated with %TT change. Conclusions Obesity-associated hypogonadism is very prevalent in males with morbid obesity and is mostly reversed after sustained weight loss by bariatric surgery. Keywords Obesity. Hypogonadism. Bariatric surgery Introduction Obesity is an increasing serious public health problem. The incidence of overweight and obesity is reaching pandemic levels. In addition, overweight and obesity are associated with a high burden of specific and chronic comorbidities such as diabetes [1] and renal dysfunction [2]. During recent years, different studies have highlighted the resolution of diabetes in obese patients after treatment with bariatric surgery as well as an amelioration of renal function and other associated comorbidities [3 6]. Hypogonadism and subfertility are also other prevalent endocrine dysfunctions among

2 obese people [7 9], and its improvement after weight loss maybe another additional benefit of treatment and can be placed in this category of modifiable comorbidities associated to obesity. Obesity may directly alter gonadal function along with other comorbidities present in the obese subject, such as diabetes, which may contribute to affect sexual function [7 9]. There are a few published reports evaluating the effect of sustained weight loss on sexual hormones in male morbidly obese patients [defined by body mass index (BMI) higher than 40 kg/m 2 ]. Most of them have found that obese males show decreased sexual quality of life, reduced fertility, and hormonal changes including decreased testosterone levels (both free and total), increased estradiol in comparison to the general population [10 14] as well as a decrease of the sex hormone binding globulin (SHBG) [11 13]. The changes of gonadotropin serum levels observed in obesity are more controversial but inappropriate normal levels [12 17], suggesting a hypogonadotropic hypogonadism situation is generally found. It has been suggested that obesity-associated male hypogonadism is related to the central inhibition of gonadotropin secretion, but the mechanisms are yet unknown. One hypothesis is that hypothalamic GnRH secretion may be inhibited by the increased estradiol from excessive peripheral conversion of testosterone in the adipose tissue. However, not all studies have shown a decrease in estradiol levels after weight loss [17, 18]. On the other hand, inhibin B and anti-müllerian hormone (AMH), which reflect Sertoli cell function, have been less explored in male obesity. Our aim was to analyze whether androgenic hormonal profile is ameliorated in morbidly obese males after substantial weight loss with bariatric surgery treatment. Patients and Methods Patients Thirty-three patients with morbid obesity that underwent bariatric surgery (25 Roux-en-Y gastric bypass and 7 sleeve gastrectomy) were included in our study. All studied patients were evaluated with standardized medical history following the institutional protocol for bariatric surgery. BMI was calculated as weight in kilograms divided by height per square meter. Waist circumference was measured at the top of the iliac crest by the same endocrinologist. Demographic and clinical data, including age, history of diabetes, and hypertension, were recorded in all subjects before bariatric surgery and at 12 months of followup. All diabetic patients were on metformin treatment and achieved good glycemic control. The percentage of weight loss was calculated as the percentage of quotient between the difference of initial weight and 12-month weight divided by the initial weight. Exclusion criteria were the presence of specific endocrine disorder affecting sexual function such as hyperprolactinemia and primary testicular disease as well as thyroid dysfunction. None of the patients were receiving androgenic hormonal treatment at the time of the study. Diabetes and hypertension were defined according to ATP criteria [19]. The study was approved by the institutional ethics committee in accordance with the Declaration of Helsinki and all participants gave their written informed consent prior to inclusion. Bariatric surgery (gastric bypass and sleeve gastrectomy) was performed as previously described briefly [20, 21]. Measurements Biochemical Measurements Blood samples were drawn by venipuncture between 0700 and 0800 hours after an overnight fast. Plasma glucose, total cholesterol, high density lipoprotein (HDL) cholesterol, and triglycerides were measured by routine clinical chemistry immediately after extraction. Non-HDL cholesterol was calculated as the difference between total cholesterol and HDL cholesterol. HbA1c was measured in blood samples with EDTA by HPLC using a fully automated Adams Menarini HI-AUTO A1c 8160 analyzer manufactured by Arkray (Kyoto, Japan) with an inter-assay coefficient of variation (CV) of 1.8 and 1.5 % at HbA1c levels of 4.8 and 9.0 %, respectively (reference range %). Serum samples for the remaining biochemical measurements were immediately frozen and stored at 80 C until assayed and were analyzed together under the same analytical conditions. Hormonal Measurements Immunoreactive insulin levels were determined using an automated electrochemiluminiscence immunoassay (Modular E, Roche Diagnostics GmbH, Mannheim, Germany); the analytical sensitivity was 0.2 mui/l and the inter-assay coefficient of variation was <2.8 %. Insulin resistance was assessed by using the homeostasis model assessment of insulin resistance (HOMA-IR) and calculated with fasting glucose and insulin by the following formula: HOMA-IR index 0 fasting insulin (mui/l) fasting glucose (mmol/l) / Serum total testosterone (TT), SHBG, estradiol, prolactin, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) concentrations were all measured by an automated electrochemiluminiscence immunoassay (Modular E, Roche Diagnostics GmbH); the functional sensitivity for TT was 12 ng/dl; the intra-assay and inter-assay coefficients of variation were <2.7 and <5.6 %. SHBG analytical sensitivity was 0.35 nmol/l; the inter-assay coefficient of variation was <4.0 %; male reference range was nmol/l. Free testosterone (FT) was calculated using the Vermeulen formula [22] with a reference range of

3 pg/ml. Estradiol functional sensitivity was 12 pg/ml; the interassay coefficient of variation was <6.2 %; male reference range was pg/ml. LH analytical sensitivity was 0.10 miu/ ml; the inter-assay coefficient of variation was <2.2 %; male reference range was miu/ml. FSH analytical sensitivity was 0.10 miu/ml; the inter-assay coefficient of variation was <5.3 %; male reference range was mui/ml. Prolactin analytical sensitivity was 0.5 ng/ml; the inter-assay coefficient of variation was <5.5 %; male reference range was ng/ml. AMH was measured by an ELISA (AMH Gen II, Beckman Coulter, Inc., Brea, CA, USA). Sensitivity of the assay was 0.16 ng/ml. The intra-assay and inter-assay CVs were <5.4 and <5.6 %, respectively. Male reference range was ng/ml. Inhibin B was measured by an ELISA (Inhibin B Gen II, Beckman Coulter, Inc.). Sensitivity of the assay was 4.8 pg/ml. The intra-assay and inter-assay CVs were <3.8 and <5.6 %. Male reference range was pg/ml. Definition of Hypogonadism Hypogonadism was considered at different cut-off values of total testosterone: moderate hypogonadism when TT was lower than 300 ng/dl and severe hypogonadism for situations in which total testosterone was lower than 200 ng/dl according to the guidelines of the Endocrine Society. Additionally, a FT criterion was also used and hypogonadism was considered for values lower than 65 pg/ml according to the normal reference range of our laboratory. Statistical Analysis Descriptive statistics were expressed as mean ± SD or median (interquartile range). Departure from normality was assessed by the Kolmogorov Smirnov test. Differences between baseline and groups weretestedbythepaired Student s t test or the nonparametric Wilcoxon test rank test as appropriate. Categorical variables were analyzed with the chi-square test. Associations between variables were estimated using Spearman s correlation coefficient. A lineal regression analysis was performed for the change of testosterone after surgery as the dependent variable including those variables that showed a significant association in the univariate analysis. A logistic regression model was also performed for identification of those factors influencing hypogonadism as the dummy variable. A p value less than 0.05 was considered as statistically significant. Data were analyzed using the SPSS 12.0 statistical package. Results The mean age of the subjects was 40.5±9.9 years and the mean presurgical BMI was 50.3±6.1 kg/m 2. Preoperatively, 5 patients had diabetes and 13 had hypertension. Anthropometric and hormonal characteristics are shown in Table 1. Hypogonadism at Baseline Prevalence of hypogonadism at baseline defined with TT<300 ng/dl was 78.8 % (26/33 patients). These patients had a significantly higher BMI (51.5±5.9 vs. 45.8±4.6 kg/m 2, p00.02) than those without hypogonadism at baseline. Also, these 26 subjects had a significantly lower prolactin level compared to those with normal TT [7.3 ( ) vs ( ) ng/ml, p00.007]. No other differences at baseline in age and the remaining studied hormones including gonadotropins, estradiol, SHBG, inhibin B, and AMH were detected in individuals with normal or low TT. Among the 26 patients with low TT, in 10, TT was <200 ng/dl, and in all those 10 subjects, FT was <65 pg/ml. In six patients in which total testosterone was <300 but >200 ng/dl, FT was low and in one case FT was low and TT>300 ng/dl. Thus, hypogonadism defined by a FT<65 pg/ml showed a prevalence of 51.5 % (17/33) before surgery. These 17 patients were older than those with normal FT (45.4±8.3 vs. 35.2±9 years, p00.003). In addition, inhibin B (92.2±47.4 vs ±58.4 pg/ml, p00.02) and AMH (2.9±1.9 vs. 5.7± 4.2 ng/ml, p00.001) serum concentrations were significantly lower in this group than in patients with normal FT. Mean LH and FSH serum concentrations showed normal inappropriate values of 3.7 ( miu/ml) and 3.1 ( miu/ml), respectively, in this group. Increased FSH and LH were detected only in one and in 3 out of the 17 subjects with FT<65 pg/ml, indicating an appropriate gonadotropin response to low testosterone. On the other hand, at baseline, only one and two patients had inhibin B and Table 1 Clinical and analytical characteristics of patients before surgery N 33 Gastric bypass/sleeve gastrectomy, n (%) 26/7 (78.8/21.2) Age, years 40.5±9.9 Weight, kg 157.9±23.5 Body mass index, kg/m ±6.1 Hypertension, n (%) 13 (39.4) Diabetes, n (%) 5 (15.2) Cardiovascular disease, n (%) 4 (12.1) Glucose, mmol/l 5.9±2.1 Glycated hemoglobin (%) 5.8±1.6 Insulin, mu/l 21.4±10.3 Total cholesterol, mmol/l 4.7±1.01 HDL cholesterol, mmol/l 0.84±0.21 Triglycerides, mmol/l 1.6±0.6

4 AMH below the reference range (25 pg/ml and 1.3 ng/ml, respectively). When diabetic subjects were considered as a separate group (n05), some differences were found as SHBG was higher (31.1±19.9 vs. 15.7±8.3 nmol/l, p00.03) and FT was lower (43.7±15 vs. 70.7±23.3 pg/ml, p00.009) than in nondiabetic obese patients at baseline. Age, BMI, and the rest of the studied hormonal parameters were similar in diabetic and nondiabetic patients. Baseline univariate correlations between hormonal parameters and age are shown in Table 2. BMI correlated with gonadal hormones and LH, as well as with SHBG, and age correlated with AMH and FT and TT. Table 3 shows the analysis of those factors predicting hypogonadism (defined by FT<65 pg/ml) in the studied subjects before surgery by using a stepwise regression analysis. Hypogonadism in obese men was significant and independently predicted by age (OR01.2, p00.01), BMI (OR01.3, p00.03), and AMH concentrations (OR00.4, p00.03) after adjustment by the remaining studied hormones (estradiol, SHBG, LH, FSH, and inhibin B). Reversal of Hypogonadism After 12 Months of Weight Loss Induced by Bariatric Surgery The mean percentage of excess weight loss (%EWL) and of weight loss was 67.8±14.2 and 18.8±5.2 %, respectively, corresponding to a mean weight loss of 59.1±17.3 kg. The percentage weight loss was similar between the two surgical techniques used (bypass vs. sleeve gastrectomy data not shown). There was a significant increase in TT and FT, SHBG, and FSH serum concentrations and a significant decrease of estradiol and prolactin after 12 months of weight loss induced by bariatric surgery in most (94 %) of the subjects as Table 3 Multivariate logistic regression analysis for factors associated to hypogonadism at baseline in morbidly obese men Odds ratio (95 % CI) p value Baseline hypogonadism Age 1.2 ( ) 0.01 Baseline BMI 1.3 ( ) 0.03 AMH 0.4 ( ) 0.03 Multiple logistic regression was performed using hypogonadism (defined by testosterone<65 pg/ml) as the dependent variable and age, baseline BMI, baseline gonadal hormones (estradiol, SHBG, LH, FSH, inhibin B, and AMH), and diabetes or impaired fasting glucose as confounders. Data are expressed as odds ratio (95 % confidence interval) BMI body mass index, AMH anti-müllerian hormone shown in Table 4. LH concentrations showed a nonsignificant increase. Figure 1 represents individual changes in FT concentrations in the 33 obese patients studied. Thus, the persistence of hypogonadism 1 year after surgery defined by TT<300 ng/dl was 6 % (2/33 patients) and 15 % (5/33) when defined by a FT<65 pg/ml. In these patients with persistent low FT 1 year after surgery, inhibin B (63.9± 33.7 vs. 92.3±55.8 pg/ml, p00.08) and AMH (1.7±1.3 vs. 2.3±1.7 ng/ml, p00.2) did not increase. When inhibin B and AMH were considered separately, the single patient presenting a low absolute value of inhibin B before surgery did not show normalization after treatment, while the one single patient with low AMH at baseline recovered 12 months after surgery. No differences were found at baseline in age, BMI, and the rest of the hormones between individuals recovering from hypogonadism and those not recovering. In individuals with normal gonadal function previous to surgery, no single case showed a hypogonadal status 1 year after surgery. Table 2 Univariate correlations (Spearman s correlation coefficient) between age, body mass index, and hormonal parameters analyzed in obese men before bariatric surgery BMI AMH Inhibin B SHBG TT FT Estradiol LH FSH PRL Age BMI * 0.5* * 0.4* AMH 0.8** * 0.6** * Inh B * * 0.4* SHBG 0.5* * TT 0.7** * * FT * E LH 0.7** 0.6* 0.02 FSH PRL 0.03 BMI body mass index, AMH anti-müllerian hormone, InhB inhibin B, TT total testosterone, FT free testosterone, E estradiol *p<0.05; **p<0.001

5 Table 4 Serum sex hormones concentrations before and after surgically induced weight loss Values are means ± SD or median (interquartile range) BMI body mass index, AMH anti-müllerian hormone Variable Preoperative 1 year postoperative p % of variation BMI (kg/m 2 ) 50.3± ±4.7 < ±5.2 Total testosterone ( ng/dl) 248.1± ±165.5 < ±97.9 Free testosterone ( pg/ml) 66.3± ±31.3 < ( 28 to 273.7) SHBG ( nmol/l) 18.3± ±18.1 < ±97.5 Estradiol ( pg/ml) 42.3± ±7.6 < ( 39 to 43.8) FSH ( mui/ml) 3.2 ( ) 5.3 ( ) < ( 23 to 188) LH ( mui/ml) 4.4 ( ) 5.1 ( ) 0.8 5( 53 to 308) Prolactin ( ng/ml) 8 ( ) 5.4 ( ) ( 92 to 220) Inhibin B (25 25 pg/ml) 115.1± ± ( 26.8 to 112.9) AMH ( ng/ml) 4.3± ± ( 74.5 to 24.7) Diabetic patients showed a similar percentage of weight loss and in the changes of studied hormonal parameters (data not shown). Finally, similar results were obtained when the two surgical techniques (bypass vs. sleeve gastrectomy) were analyzed separately. Age was significantly associated with AMH (r0 0.4, p00.03) and FT (r0 0.4, p0 0.01) serum concentrations after weight loss, thus indicating that younger subjects recovered better from presurgical hypogonadal status. The percentage of weight loss was significant and negatively associated with the percentage of changes of SHBG (r0 0.4, p00.04), inhibin B (r0 0.4, p00.03), and AMH (r0 0.4, p00.01), but not with the percentage of TT and FT change. The positive correlation observed between FT and AMH at baseline persisted 12 months after bariatric surgery (r00.4, p00.02). Also, the negative correlation of inhibin B with LH and with FSH persisted significantly after 12 months of bariatric surgery (r0 0.4, p00.03 and r0 0.7, p<0.001, respectively). Multiple Regression Analyses When performing a linear regression analysis, age and the percentage weight loss were the only independent variables significantly associated with the percentage of TT change after adjustment by baseline BMI, the percentage of weight loss and the percentage of changes of gonadal hormones (estradiol, SHBG, LH, FSH, inhibin B, and AMH), and the presence of diabetes and/or fasting glucose impairment. The results of the regression analysis using TT and FT changes as dependent variables are shown in Table 5. Fig. 1 Free testosterone serum concentrations at baseline and 12 months after bariatric surgery

6 Table 5 Multivariate lineal regression analysis for factors predicting the percentual change of FT and TT in morbidly obese men after bariatric surgery Discussion β (95 % CI) p value TT change (%) Age 0.5 ( ) Percentage weight loss 0.6 ( 11.4 to 2.4) FT change (%) Age 0.5 ( ) 0.02 SHBG 0.4 ( 0.5 to 0.04) 0.05 Percentage weight loss 0.4 ( 7.4 to 0.2) 0.06 Multiple logistic regression was performed using the percentual changes of total (TT) and free testosterone (FT) as dependent variables and age, baseline BMI, weight loss, and gonadal hormone changes (estradiol, SHBG, LH, FSH, inhibin B, and AMH) as confounders. Data are expressed as β (95 % confidence interval) Our study clearly indicates that the prevalence of functional hypogonadism in males with morbid obesity is high, and weight loss obtained by surgical treatment leads to a complete recovery of gonadal function in most of the cases. This hypogonadic state in long-term obesity may have different consequences in the health and quality of life of men with morbid obesity, as it may affect sexual life but it could also contribute, among others, to an impairment of coexisting cardiovascular disorders. The evaluation of gonadal state, which has been a matter of debate in recent years due to methodological reasons, is even more complex in individuals with high fat mass [23]. Due to the fact that obese subjects have a specific scenario of insulin resistance on one side and increased testosterone to estradiol conversion on the other, SHBG and its affinity for testosterone are modified in a way that the use of TT or FT either calculated or measured may pose additional methodological problems for the interpretation of the results. Also, after bariatric surgery, a significant increase of SHBG levels is observed, which has been attributed to the dramatic fall in insulin and leptin serum levels due to the weight loss effect [24 26]. In our study, we did not observe any correlation between the changes of SHBG and insulin resistance in the pre/post-surgery situation. However, the evaluation of insulin resistance with HOMA is an imperfect indicator of insulin resistance in vivo, so it is possible that insulin resistance together with other different factors may drive such a change. Even in the presence of an increase in SHBG which would explain the increase of TT, the accompanying increase in FT indeed indicates that the recovery of gonadal function is true. Recent guidelines of the Endocrine Society dealing with the treatment of hypogonadism in men recommend making the diagnosis of hypogonadism using the lower limit of TT normal range for healthy young men established in their reference laboratory [23, 27]. In addition, these guidelines also recommend the use of calculated FT when the TT value lies near the lower limit of the normal range [23, 27]. However, there is no special mention in the guidelines of how to measure testosterone in obese men [27]. In our study when using TT, the prevalence of low values was 78.8 %, whereas when FT was calculated, it was around 50 %. Both results are clinically relevant, and taking into account the extensive methodological discussion in previous years, it is difficult to recommend the use of one or other parameters for the evaluation of gonadal function in obese male; probably both are required. However, when severe hypogonadism was considered according to TT< 200 ng/dl, virtually all subjects had simultaneous and concordant low values of FT. Our data on the prevalence of impaired gonadal function in obese men are somehow higher than the 57.7 and 35.6 % reported by Hofstra et al. [8], and this may be due to the fact that in this latter study, the diagnosis of hypogonadism was based on reference ranges of testosterone obtained from men between 20 and 60 years. Other epidemiologic studies have also established a close relationship between obesity and low T in men, showing that between 20 and 40 % of obese men have a low TT and FT serum levels, with a linear relationship with BMI [7 9, 12, 16, 18, 28, 29]. These results contrast with the prevalence of hypogonadism in the general male population which is about 4 to 5 % [30]. In view of the global epidemic of obesity, obesity-related hypogonadism is likely to be one of the most common causes for reduced serum testosterone levels, next to aging. Some other related conditions, such as metabolic syndrome or diabetes, are also associated to higher rates of low testosterone in males, ranging from 30 to 50 % [7, 9, 31, 32]. In our series, associated diabetes did not perform worse than morbid obesity without coexisting diabetes, although diabetes per se may play a role in impaired gonadal function as even nonobese diabetic subjects may show some degree of hypogonadism [7, 9, 32]. The hormonal gonadal profile in our subjects and in most reports [8, 10, 14 17, 28, 29] clearly indicates that the origin of the perturbed production of gonadal steroids is driven at the central level. Thus, gonadotropins are inadequately found in the normal range while circulating testosterone is low. The central nature of this disgovernance is however influenced by a number of peripheral signals that are disturbed in extremely obese individuals, the first one being an increased conversion of testosterone to estradiol in the fatty visceral and subcutaneous mass. In our study, estradiol levels were higher before surgery when compared to controls, and moreover, a normalization of estradiol was observed in most subjects after 1 year of bariatric surgery. This does not mean that other factors may not participate in the functional hypogonadotropic hypogonadism observed in

7 obesity, and it is very likely that the leptin resistance state associated to obesity may in fact also contribute to a lower LH secretion. Also, the central action of leptin involves the activation of the Kisspeptin pathway [34, 35] which directly contributes to an increase in the GnRH activity. The demonstration of this process is very difficult in human obesity due to the inaccessibility for exploring this pathway in humans. And finally, besides its central effect, leptin may also act at the Leydig cell level, where leptin receptors have been identified [24, 33]. To our knowledge, this is the first study evaluating concurrently the changes in gonadal steroids together with Sertoli function in morbidly obese men after bariatric surgery. As for Sertoli cell function, inhibin B and AMH did not show a particular alteration before surgery, as only 2 out of the 33 subjects showed decreased AMH and only one case with low inhibin B. In contrast to the fact that most of the subjects recovered to normal testosterone concentrations 1 year after surgery, AMH concentrations did not change after surgery, but inhibin B showed a significant correlation with the loss of BMI and a trend was observed indicating higher inhibin B concentrations after weight loss. It is also striking that in the two cases in which both hormones were decreased at baseline, a complete normalization was observed after surgery. Thus, although the clinical consequences of Sertoli cell dysfunction are not well known as a decreased spermatogenesis in obese men has not been proven [36, 37], weight loss tends also to normalize Sertoli cell hormones in those cases in which an alteration is observed prior to successful bariatric surgery. The reported results in relation to changes of AMH and inhibin B are somehow scanty and contradictory [13, 17, 38] as some investigators found an AMH increase in relation to weight loss [38]; this issue will require further investigation. Hypogonadism is a peculiar feature of abdominal obesity that independently predicts the development of insulin resistance and diabetes mellitus [9, 32]. The treatment of male hypogonadism is well established when FT is <180 pmol/ l (52 pg/ml). However, despite the increasing prevalence of obesity in men, recent guidelines on male hypogonadism do not discuss the issue of obesity-related hypogonadism, when and how to treat if detected [27, 39]. Male hypogonadism in obesity is a special clinical unsolved situation, because the substitutive hormonal therapy with testosterone is likely to cause a substantial rise in estradiol. On the other hand, treatment with inhibitors of estrogen biosynthesis (through administration of the aromatase inhibitor testolactone) has demonstrated to improve hypogonadotropic hypogonadism in obese male subjects suggesting an inhibitory role of peripheral estrogen in the hypothalamo-pituitary axis [40]. However, such a treatment is far to be recommended due to the lack of confirmatory and safety long-term data. Our study has some limitations. The major limitation was sample size, resulting in wide confidence intervals, and the results must therefore be complemented and confirmed with those of other series. We did not evaluate sexual dysfunction to correlate the clinical improvement with hormones changes. However, sexual dysfunction in obese patients is a multifactorial condition, and other coexisting comorbidities like diabetes or hypertension and probably psychological factors may also be implicated. In conclusion, obesity-associated hypogonadism is a very prevalent situation in males with morbid obesity, and its nature seems to be hypogonadotropic and is mostly reversed with weight loss, especially by bariatric surgery. Unless persistence of low TT and FT is not confirmed after a substantial weight loss, substitutive treatment after a more careful etiological gonadal study is not recommended. The reversibility of hypogonadism after weight loss by bariatric surgeryinmorbidlyobesemensupportsevenmorethe indication of this kind of treatment. Conflict of interest The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported. References 1. Narayan KM, Boyle JP, Thompson TJ, et al. Effect of BMI on lifetime risk for diabetes in the U.S. Diabetes Care. 2007;30: Serra A, Romero R, Lopez D, et al. Renal injury in the extremely obese patients with normal renal function. Kidney Int. 2008;73: Buchwald H, Estok R, Fahrbach K, et al. Weight and type 2 diabetes after bariatric surgery: systematic review and meta-analysis. Am J Med. 2009;122: Sjöström L, Lindroos AK, Peltonen M, et al. Swedish Obese Subjects Study Scientific Group lifestyle, diabetes, and cardiovascular risk factors 10 years after bariatric surgery. N Engl J Med. 2004;351: Navarro-Díaz M, Serra A, Romero R, et al. Effect of drastic weight loss after bariatric surgery on renal parameters in extremely obese patients: long-term follow-up. J Am Soc Nephrol. 2006;17:S Serra A, Granada ML, Romero R, et al. The effect of bariatric surgery on adipocytokines, renal parameters and other cardiovascular risk factors in severe and very severe obesity: 1-year follow-up. Clin Nutr. 2006;25: Dhindsa S, Miller MG, McWhirter CL, et al. Testosterone concentrations in diabetic and nondiabetic obese men. Diabetes Care. 2010;33: Hofstra J, Loves S, van Wageningen B, et al. High prevalence of hypogonadotropic hypogonadism in men referred for obesity treatment. Neth J Med. 2008;66: Dandona P, Dhindsa S. Update: hypogonadotropic hypogonadism in type 2 diabetes and obesity. J Clin Endocrinol Metab. 2011;96: Dallal RM, Chernoff A, O'Leary MP, et al. Sexual dysfunction is common in the morbidly obese male and improves after gastric bypass surgery. J Am Coll Surg. 2008;207: Reis LO, Favaro WJ, Barreiro GC, et al. Erectile dysfunction and hormonal imbalance in morbidly obese male is reversed after

8 gastric bypass surgery: a prospective randomized controlled trial. Int J Androl. 2010;33: Giagulli VA, Kaufman JM, Vermeulen A. Pathogenesis of the decreased androgen levels in obese men. J Clin Endocrinol Metab. 1994;79: Aggerholm AS, Thulstrup AM, Toft G, et al. Is overweight a risk factor for reduced semen quality and altered serum sex hormone profile? Fertil Steril. 2008;90: Hammoud A, Gibson M, Hunt SC, et al. Effect of Roux-en-Y gastric bypass surgery on the sex steroids and quality of life in obese men. J Clin Endocrinol Metab. 2009;94: Bastounis EA, Karayiannakis AJ, Syrigos K, et al. Sex hormone changes in morbidly obese patients after vertical banded gastroplasty. Eur Surg Res. 1998;30: Alagna S, Cossu ML, Gallo P, et al. Biliopancreatic diversion: long-term effects on gonadal function in severely obese men. Surg Obes Relat Dis. 2006;2: Globerman H, Shen-Orr Z, Karnieli E, et al. Inhibin B in men with severe obesity and after weight reduction following gastroplasty. Endocr Res. 2005;31: Strain GW. Zumoffb, Miller LD et al. Effect of massive weight loss on hypothalamic pituitary gonadal function in obese men. J Clin Endocrinol Metab. 1988;66: National Cholesterol Education Program (NCEP). Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 2002;106: Deitel M, Crosby RD, Gagner M. The First International Consensus Summit for sleeve gastrectomy (SG), New York City, October 25 27, Obes Surg. 2008;18(5): Pérez-Romero N, Serra A, Granada ML, et al. Effects of two variants of Roux-en-Y gastric bypass on metabolism behaviour: focus on plasma ghrelin concentrations over a 2-year follow-up. Obes Surg. 2010;20: Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84: Rosner W, Auchus RJ, Azziz R, et al. Position statement: utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab. 2007;92: Isidori AM, Caprio M, Strollo F, et al. Leptin and androgens in male obesity: evidence for leptin contribution to reduced androgen levels. J Clin Endocrinol Metab. 1999;84: Pasquali R, Casimirri F, De R I, et al. Insulin regulates testosterone and sex hormone-binding globulin concentrations in adult normal weight and obese men. J Clin Endocrinol Metab. 1995;80: Mingrone G, Greco AV, Giancaterini A, et al. Sex hormonebinding globulin levels and cardiovascular risk factors in morbidly obese subjects before and after weight reduction induced by diet or malabsorptive surgery. Atherosclerosis. 2002;161: Bhasin S, Cunningham GR, Hayes FJ, et al. Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95: Zumoff B, Strain GW, Miller LK, et al. Plasma free and non-sexhormone-binding-globulin-bound testosterone are decreased in obese men in proportion to their degree of obesity. J Clin Endocrinol Metab. 1990;71: Rao SR, Kini S, Tamler R. Sex hormones and bariatric surgery in men. Gend Med. 2011;8: Travison TG, Araujo AB, Kupelian V, et al. The relative contributions of aging, health, and lifestyle factors to serum testosterone decline in men. J Clin Endocrinol Metab. 2007;92: Wang C, Nieschlag E. Swerdloff R et al; International Society of Andrology (ISA); International Society for the Study of Aging Male (ISSAM); European Association of Urology (EAU); European Academy of Andrology (EAA); American Society of Andrology (ASA) Investigation, treatment, and monitoring of late-onset hypogonadism in males: ISA, ISSAM, EAU, EAA, and ASA recommendations. J Androl. 2009;30: Laaksonen DE, Niskanen L, Punnonen K, et al. Testosterone and sex hormone-binding globulin predict the metabolic syndrome and diabetes in middle-aged men. Diabetes Care. 2004;27: Caprio M, Isidori AM, Carta AR, et al. Expression of functional leptin receptors in rodent Leydig cells. Endocrinology. 1999;140: Tena-Sempere M. KiSS-1 and reproduction: focus on its role in the metabolic regulation of fertility. Neuroendocrinology. 2006;83: Dungan HM, Clifton DK, Steiner RA. Minireview: kisspeptin neurons as central processors in the regulation of gonadotropinreleasing hormone secretion. Endocrinology. 2006;147: MacDonald AA, Herbison GP, Showell M, et al. The impact of body mass index on semen parameters and reproductive hormones in human males: a systematic review with meta-analysis. Hum Reprod Update. 2010;16: Teerds KJ, de Rooij DG, Keijer J. Functional relationship between obesity and male reproduction: from humans to animal models. Hum Reprod Updat. 2011;17: Håkonsen LB, Thulstrup AM, Aggerholm AS, et al. Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men. Reprod Health. 2011;17: Kelleher S, Conway AJ, Handelsman DJ. Blood testosterone threshold for androgen deficiency symptoms. J Clin Endocrinol Metab. 2004;89: Zumoff B, Miller LK, Strain GW. Reversal of the hypogonadotropic hypogonadism of obese men by administration of the aromatase inhibitor testolactone. Metabolism. 2003;52: