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Flashcards in Endocrine - Physiology Deck (60)
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1

What does this hypothalamic hormone induces/inhibits: TRH

+ TSH, prolactin

2

What does this hypothalamic hormone induces/inhibits: Dopamine

- Prolactin

3

What does this hypothalamic hormone induces/inhibits: CRH

+ ACTH, MSH, beta-endorphin

4

What does this hypothalamic hormone induces/inhibits: GHRH

+ GH

5

What does this hypothalamic hormone induces/inhibits: Somatostatin

- GH, TSH

6

What does this hypothalamic hormone induces/inhibits: GnRH

+ FSH, LH

7

What does this hypothalamic hormone induces/inhibits: Prolactin

- GnRH

8

Describe prolactin regulation

Prolactin is tonically inhibited by dopamine from hypothalamus

It inhibits own secretion by increasing dopamine synthesis and secretion

TRH also increases prolactin secretion

9

Function of Prolactin (2)

1. Stimulates milk production in breast

2. Inhibits ovulation/spermatogenesis by inhibiting GnRH synthesis and release

10

What pharmacological substances can promote or inhibit prolactin secretion?

Inhibit prolactin: dopamine agonist (bromocriptine)

Promote prolactin: dopamine antagonists (most antipsychotics), estrogens (OCPs, pregnancy) stimulate prolactin secretion

11

Functions of growth hormone (2)

1. Stimulates linear growth and muscle mass through IGF1/somatomedin secretion
2. increases insulin resistance (diabetogenic)

12

Regulation of growth hormone. What promotes or inhibits secretion?

Released in pulses in response to GHRH

Promoted by exercise, sleep
Inhibited by glucose, somatostatin

13

In the first step of adrenal steroids, what is cholesterol converted to, facilitated by what enzyme?

Cholesterol to Pregnenolone
by Desmolase

14

What can promote or inhibit desmolase activity?

ACTH +
Ketoconazole -

15

Function of 17alpha-hydroxylase

1. Pregnenolone -> 17-hydroxypregnenolone
2. Progesterone -> 17-hydroxyprogesterone

16

Function of 3beta-hydroxysteroid dehydrogenase

1. Pregnenolone -> Progesterone
2. 17-hydroxypregnenolone -> 17-hydroxyprogesterone
3. DHEA -> Androstenedione

17

Function of 21-hydroxylase

1. Progesterone -> 11-deoxycorticosterone
2. 17-hydroxyprogesterone -> 11-deoxycortisol

18

Function of 11beta-hydroxylase

1. 11-deoxycorticosterone -> Corticosterone
2. 11-deoxycortisol -> Cortisol

19

Function of aromatase

1. Androstenedione -> estrone
2. Testosterone -> estradiol

20

Function of 5alpha-reductase

Testosterone -> DHT

21

Function of Aldosterone synthase

Corticosterone -> Aldosterone
Activated by Angiotensin II

22

Describe level adrenal steroids in: 17alpha-hydroxylase deficiency

Mineralcorticoid: High
Cortisol: Low
Sex hormone: Low

Presentation: hypertension, hypokalemia
XY: pseudohermaphroditism (low DHT)
XX: lacks secondary sex characteristics

23

Describe level adrenal steroids in: 21-hydroxylase deficiency

Mineralcorticoid: Low
Cortisol: Low
Sex hormone: High

Presentation: hypotension, hyperkalemia, high renin, volume depletion
Masculinization; pseudohermaphroditism in females

24

Describe level adrenal steroids in: 11beta-hydroxylase deficiency

Mineralcorticoid: High (11-deoxycorticosterone)
Cortisol: Low
Sex hormone: High

Presentation: Masculinization

25

Why do all congenital adrenal enzme deficiencies have enlargement of both adrenal glands?

Increased ACTH from low cortisol

26

What is cortisol bound to?

Corticosteroid-binding globulin (CBG)

27

Functions of cortisol (6)

1. maintains blood pressure (upregulates alpha1-receptors on arterioles which increases sensitivity to NE/E)

2. decreases bone formation

3. anti-inflammatory/immunosuppressive

4. increases insulin resistance (diabetogenic)

5. Increases gluconeogensis, lipolysis, proteolysis (during stress)

6. inhibits fibroblasts (causes striae)

28

What is impact of chronic stress on HPA axis?

Prolonged secretion

29

Describe cortisol regulation

CRH (hypothalamus) stimulates ACTH release (pituitary), causing cortisol production in adrenal zona fasciculata.

Excess cortisol suppresses CRH, ACTH and cortisol secretion

30

Cortisol effects on the immune system (5)

1. Inhibits production of leukotrienes/prostaglandins

2. inhibits leukocyte adhesion (neutrophilia)

3. blocks histamine release from mast cells

4. reduces eosinophils

5. blocks IL-2 production