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Flashcards in Endocrine - Physiology Deck (95)
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1

What is the effect of thyrotropin-releasing hormone on pituitary hormone secretion?

It stimulates thyroid-stimulating hormone and prolactin secretion

2

What is the effect of dopamine on pituitary hormone secretion?

Inhibition of prolactin secretion

3

What is the effect of corticotropin-releasing hormone on pituitary hormone secretion?

It stimulates adrenocorticotropic hormone secretion

4

What is the effect of growth hormone-releasing hormone on pituitary hormone secretion?

It stimulates growth hormone secretion

5

What is the effect of somatostatin on pituitary hormone secretion?

It inhibits growth hormone and thyroid-stimulating hormone secretion

6

What is the effect of gonadotropin-releasing hormone on pituitary hormone secretion?

It stimulates luteinizing hormone and follicle-stimulating hormone secretion

7

What is the effect of prolactin on pituitary hormone secretion?

It inhibits gonadotropin-releasing hormone, which in turn decreases luteinizing hormone and follicle-stimulating hormone secretion

8

How does prolactin provide negative feedback to its own secretion?

High prolactin levels cause increased dopamine synthesis and secretion by the hypothalamus

9

Why might bromocriptine be withheld from a woman who is trying to breast feed?

Bromocriptine is a dopamine agonist, and so it inhibits prolactin secretion

10

A woman being treated for schizophrenia complains of breast fullness and amenorrhea; what is the likely cause?

Increased prolactin levels secondary to dopamine antagonists (antipsychotics)

11

Why are women less likely to become pregnant when breastfeeding?

Prolactin inhibits ovulation via the inhibition of gonadotropin-releasing hormone

12

A woman has had her thyroid surgically removed and is not taking thyroid hormone replacement. She now complains of amenorrhea; what is the likely cause?

She has hypothyroidism, which can cause prolactin release and thus amenorrhea

13

How does prolactin affect fertility in men?

It decreases spermatogenesis by inhibiting gonadotropin-releasing hormone synthesis and release

14

Which enzyme is responsible for converting cholesterol to pregnenolone?

Desmolase

15

Which enzyme catalyzes conversion of testosterone to dihydrotestosterone?

5-reductase

16

Adrenocorticotropic hormone has a(n) _____ (inhibitory/stimulatory) effect on desmolase whereas ketoconazole has a(n) _____ (inhibitory/stimulatory) effect on desmolase.

Stimulatory; inhibitory

17

What enzyme is responsible for the conversion of pregnenolone to progesterone?

3-hydroxysteroid dehydrogenase

18

What is the effect of congenital adrenal enzyme deficiencies on adrenal size?

Decreased cortisol production and loss of negative feedback causes increased adrenocorticotropic hormone stimulation leading to bilateral adrenal enlargement

19

Which enzyme catalyzes the conversion of testosterone to estradiol?

Aromatase

20

What stimulates aldosterone synthase to convert corticosterone into aldosterone?

Angiotensin II stimulates aldosterone synthase

21

A patient has decreased sex hormone and cortisol levels and increased mineralocorticoid levels; what is the diagnosis?

17-hydroxylase deficiency

22

What are the symptoms associated with 17-hydroxylase deficiency?

Hypertension and hypokalemia (due to increased mineralocorticoids)

23

What is the phenotype of XY males who have 17-hydroxylase deficiency?

Pseudohermaphroditism; decreased dihydrotestosterone means that male secondary sex characteristics do not develop

24

Do XY males with 17-hydroxylase deficiency have male or female internal anatomy?

Male; these patients still make müllerian inhibitory factor, which leads to development of the male internal reproductive tract

25

What is the phenotype of XX females who have 17-hydroxylase deficiency?

Externally female, but they lack secondary sexual characteristics ("sexual infantilism") due to decreased testosterone

26

A patient has increased sex hormones, decreased cortisol and mineralocorticoids, and HYPOtension; what is the diagnosis?

21-hydroxylase deficiency

27

What symptoms are associated with 21-hydoxylase deficiency?

Masculinization, female pseudohermaphotidism, hypotension, hyperkalemia, salt wasting, increased plasma renin activity, and volume depletion

28

What is the phenotype of XX females who have 21-hydroxylase deficiency?

The deficiency shunts precursors to the sex hormone pathway, increasing dihydrotestosterone, which causes masculinization and androgenization of external female genitalia

29

A female infant is born with ambiguous genitalia and is found to be severely hypotensive; what is the diagnosis?

21-hydroxylase deficiency causes hyperreninemic hypoaldosteronism and salt wasting, resulting in hypotension and hyperkalemia

30

A patient has increased sex hormones, decreased cortisol, aldosterone, and mineralocorticoids, and has HYPERtension; what is the diagnosis?

11-hydroxylase deficiency