HYPOTHALAMUS - ANTERIOR PITUITARY CONNECTION. Releasing Hormones

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1 HYPOTHALAMUS - ANTERIOR PITUITARY CONNECTION Releasing Hormones

2 Hypothalamus-Anterior Pituitary Connection Produces hormones called Releasing Hormones that control the production and release of the tropic hormones by the anterior pituitary Hypothalamus

3 Releasing Hormones 1. Corticotropic Releasing Hormone (CRH) CRH ACTH ( = stimulates) 2. Thyrotropic Hormone Releasing Hormone (TRH) TRH TSH 3. Somatostatin Somatostatin growth hormone ( = inhibits) 4. Growth Hormone Releasing Hormone (GHRH) GHRH growth hormone

4 Releasing Hormones (con t) 5. Gonadotropin Hormone Releasing Hormone (GnRH) GnRH GnRH LH FSH Problem: Pattern of LH and FSH release is not identical. How can they be different? Inhibin FSH

5 Releasing Hormones (con t) 6. Dopamine Dopamine prolactin 7. Prolactin Stimulating Hormone (PSH) PSH prolactin

6 Negative Feedback Hormone A Hormone B

7 Negative Feedback GnRH LH GnRH LH Estrogen (moderate)

8 LH, FSH and GnRH GnRH GnRH inhibin LH FSH LH FSH FSH GnRH GnRH

9 Estrogen/GnRH Very low estrogen moderate estrogen very high estrogen GnRH GnRH GnRH

10 Positive Feedback Hormone A Hormone B GnRH LH very high estrogen

11 LH FSH E Prog Ovarian Cycle Follicular Luteal Mns. Prolif. Secretory Uterine Cycle

12 Estrogen (Estradiol) Levels across the Monthly Cycle 1. Levels start to increase on Day 1 and gradually increase throughout the preovulatory phase. 2. Surge (sharp increase) 24 hours prior to ovulation. 3. Levels decrease after surge (through ovulation).

13 Estrogen (Estradiol) Levels across the Monthly Cycle 4. Levels rise during the postovulatory phase as the corpus luteum develops. 5. Drop off just before menses when the corpus luteum dies but not too dramatically because follicles start growing at the same time the corpus luteum is dying.

14 Estrogen Progesterone Day 1 Ovulation Day 1

15 Progesterone Levels across the Monthly Cycle 1. Levels low on Day Stay very low throughout the preovulatory phase. 3. Increase during the postovulatory phase with the development of the corpus luteum. 4. Drop off just before menses with the death of the corpus luteum.

16 Estrogen Progesterone Day 1 Ovulation Day 1

17 FSH Levels across the Monthly Cycle 1. Begin to rise at the end of the postovulatory phase (before Day 1). 2. Decrease in late preovulatory phase. 3. Surge at the time of ovulation. 4. Decrease after ovulation and stays low throughout most of the postovulatory phase.

18 FSH LH Day 1 Ovulation Day 1

19 LH Levels across the Monthly Cycle 1. Begin to increase on Day Rise to moderate level and stay relatively steady for the rest of the preovulatory phase. 3. Surge on the day of ovulation. 4. Declines right after ovulation. 5. Increases toward the end of the luteal phase and then declines again.

20 FSH LH Day 1 Ovulation Day 1

21 ADRENAL GLAND & ENDOCRINE POTPOURRI

22 Adrenal Gland Adrenal Medulla Adrenal Cortex The adrenal gland is made up of two, simultaneously present but independent glands.

23 Adrenal Medulla Gland at inner core of adrenal May or may not be an actual endocrine gland produces adrenaline and noradrenaline in response to stress

24 Adrenal Cortex Outer gland of adrenal produces and releases hormones in response to stimulation from the tropic hormone, ACTH CRH ACTH adrenal cortical hormones

25 Adrenal Cortex Produces and releases: glucocorticoids: control glucose metabolism and food intake Cortisol is the major glucocorticoid in humans mineralocorticoids: regulate levels of minerals and electrolytes such as sodium or potassium Aldosterone is the major mineralocorticoid in humans

26 Adrenal Cortex Produces and releases: sex steroids - estrogen, progesterone and androgen estrogen and progesterone produced by the adrenal cortex of women is insignificant compared to that coming from ovary ADRENAL CORTEX IS THE MAJOR SOURCE OF ANDROGEN FOR WOMEN

27 Androgens Testosterone best known androgen very strong or potent androgen most prevalent androgen found in men

28 Androgens Androstenedione much less well known than testosterone weaker or less potent androgen than testosterone most prevalent androgen found in women

29 Androgens Androstenedione converted to testosterone by specific target tissue allows for localized powerful androgen actions without total masculinization of the female body

30 Actions of Androgens Stimulates the growth of pubic and underarm hair acne control of sex drive

31 Two Main Types of Hormones Peptide hormones Water soluble hormones Large molecules made up of long chains of amino acids Cannot cross the blood-brain barrier ADH, oxytocin, most releasing hormones and the tropic hormones fall into this category

32 Two Main Types of Hormones Steroid Hormones Fat soluble hormones Smaller molecular structures than peptide hormones Typically can cross the blood-brain barrier Include estrogens, androgens, progesterone, glucocorticoids, mineralocorticoids

33 Production of Sex Steroids Cholesterol is the precursor from which progesterone, androgen and estrogen are produced. All of these hormones are chemically very similar to each other such that receptors can be confused and respond to the wrong hormone.

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35 Sex Steroid Production Cholesterol Progesterone Androstenedione Estrial Estrone Testosterone Estradiol