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34 Cards in this Set
- Front
- Back
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What are the main steroidogenic tissues? |
1. Adrenal cortex 2. Testes 3. Ovaries |
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What is the common precursor of all steroid hormones? |
1. Cholesterol--- cyclopentanophenanthrene ring |
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What hormones do the ovary produce? |
1. Estradiol 2. Estriol 3. Estrone
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What is the rate-limiting step in the synthesis of steroid hormones? |
1. Cleavage of a 6-carbon residue from cholesterol 2. Produces pregenolone plus isocaproaldehyde |
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What enzyme is involved in the rate-limiting step of steroid synthesis? |
1. Cholesterol-20,22-desmolase |
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What does the zona glomerulosa of the adrenal gland produce? |
1. Mineralocorticoids |
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What does the zona fasciculata of the adrenal gland produce? |
1. Glucocorticoids |
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What does the zona reticular is of the adrenal cortex produce? |
1. Androgens |
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What are the four steroid hormones are produced in the adrenal gland? |
1. Cortisol (glucocorticoid) 2. Corticosterone (corticosteroid) 3. Aldosterone (mineralocorticoid) 4. Androstendione (precursor to sex hormones) |
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What enzymes, specific to steroid hormone production in the adrenals, are unique to the zona glomerulosa? |
1. 18-hydroxylase 2. 18-hydroxydehydrogenase |
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What is the transport proteins for aldosterone and cortisol? |
1. Corticosteroid binding a-globulin (CBP)-- 80% 2. Albumin--15% 3. 5-10% is "free" |
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What cells synthesize testosterone in the testes? |
1. Leydig cells |
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What is the key enzyme for testosterone synthesis? |
1. 17B-hydroxysteroid dehydrogenase |
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What is the rate-limiting step in testosterone synthesis? What stimulates this step? |
1. STAR 2. Stimulated by LH |
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What is STAR? |
1. Steroidogenic acute regulatory protein 2. Involved in rate-limiting step in testosterone synthesis |
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What converts testosterone to dihydrotestosterone (DHT)? |
1. 5a-reductase 2. NADPH is cofactor |
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What is so special about DHT? |
1. Much more powerful than testosterone 2. Formed in peripheral tissue, not testes
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What does a DHT deficiency lead to? |
1. Baldness |
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What produces androgen-binding protein? What stimulates its synthesis? |
1. Sertoli cells in the testes 2. Testosterone and FSH |
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How is testosterone production regulated? |
1. GnRH released from hypothalamus, acts on pituitary 2. LH and FSH are released from pituitary 3. LH acts on leydig cells and stimulates testosterone production 4. FSH acts on sertoli cells in seminiferous tubules, increases spermatogenesis |
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What do sertoli cells secrete do inhibit testosterone synthesis? |
1. Inhibin--- acts on FSH |
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What is the main estrogen of the ovary? What stimulates its synthesis? |
1. 17B-estradiol 2. Stimulated by FSH |
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What is the role of FSH and LSH in estrogen synthesis? What is in charge of negative feedback? |
1. FSH stimulates follicle development in ovary 2. LSH for ovulation
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What enzyme introduces a benzene ring in the reaction from testosterone to estradiol? |
1. Aromatase |
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On what specific structure does LH act in estrogen synthesis? |
1. Corpus luteum |
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What is the transport protein for androgens and estrogen? |
1. Sex hormone-binding globulin |
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What is the % binding of androgens? |
1. 65% testosterone bound to SHBG 2. 34% to albumin 3. 1-2% free |
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What is the % binding of estrogen? |
1. 60% estrogen boud to SHBG 2. 20% bound to albumin 3. 20% free |
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Where are sex hormones metabolized? How? |
1. Liver 2. Hormones deactivated by conjugation to glucuronic acid or sulfate--- can be excreted |
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What is the role of estrogen in pregnancy? |
1. Maintenance of pregnancy |
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What is the role of progestins in pregnancy? |
1. Mimics the action of progesterone |
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What is the role of chorionic gonadotropin in pregnancy? |
1. Similar to LH 2. Peaks in first trimester
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What is the role of placental lactogen in pregnancy? |
1. Similar to prolactin and GH |
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What is the role of relaxin in pregnancy? |
1. Produced in ovarian corpus luteum 2. Inhibits myometrial contactions 3. Secretion increases during gestation |
