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Endocrine - Physiology Flashcards

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1
Q

What does this hypothalamic hormone induces/inhibits: TRH

A

+ TSH, prolactin

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2
Q

What does this hypothalamic hormone induces/inhibits: Dopamine

A
  • Prolactin
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3
Q

What does this hypothalamic hormone induces/inhibits: CRH

A

+ ACTH, MSH, beta-endorphin

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4
Q

What does this hypothalamic hormone induces/inhibits: GHRH

A

+ GH

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5
Q

What does this hypothalamic hormone induces/inhibits: Somatostatin

A
  • GH, TSH
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6
Q

What does this hypothalamic hormone induces/inhibits: GnRH

A

+ FSH, LH

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7
Q

What does this hypothalamic hormone induces/inhibits: Prolactin

A
  • GnRH
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8
Q

Describe prolactin regulation

A

Prolactin is tonically inhibited by dopamine from hypothalamus

It inhibits own secretion by increasing dopamine synthesis and secretion

TRH also increases prolactin secretion

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9
Q

Function of Prolactin (2)

A
  1. Stimulates milk production in breast

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

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10
Q

What pharmacological substances can promote or inhibit prolactin secretion?

A

Inhibit prolactin: dopamine agonist (bromocriptine)

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

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11
Q

Functions of growth hormone (2)

A
  1. Stimulates linear growth and muscle mass through IGF1/somatomedin secretion
  2. increases insulin resistance (diabetogenic)
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12
Q

Regulation of growth hormone. What promotes or inhibits secretion?

A

Released in pulses in response to GHRH

Promoted by exercise, sleep
Inhibited by glucose, somatostatin

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13
Q

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

A

Cholesterol to Pregnenolone

by Desmolase

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14
Q

What can promote or inhibit desmolase activity?

A

ACTH +

Ketoconazole -

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15
Q

Function of 17alpha-hydroxylase

A
  1. Pregnenolone -> 17-hydroxypregnenolone

2. Progesterone -> 17-hydroxyprogesterone

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16
Q

Function of 3beta-hydroxysteroid dehydrogenase

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

Function of 21-hydroxylase

A
  1. Progesterone -> 11-deoxycorticosterone

2. 17-hydroxyprogesterone -> 11-deoxycortisol

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18
Q

Function of 11beta-hydroxylase

A
  1. 11-deoxycorticosterone -> Corticosterone

2. 11-deoxycortisol -> Cortisol

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19
Q

Function of aromatase

A
  1. Androstenedione -> estrone

2. Testosterone -> estradiol

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20
Q

Function of 5alpha-reductase

A

Testosterone -> DHT

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21
Q

Function of Aldosterone synthase

A

Corticosterone -> Aldosterone

Activated by Angiotensin II

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22
Q

Describe level adrenal steroids in: 17alpha-hydroxylase deficiency

A

Mineralcorticoid: High
Cortisol: Low
Sex hormone: Low

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

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23
Q

Describe level adrenal steroids in: 21-hydroxylase deficiency

A

Mineralcorticoid: Low
Cortisol: Low
Sex hormone: High

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

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24
Q

Describe level adrenal steroids in: 11beta-hydroxylase deficiency

A

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

Presentation: Masculinization

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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
31
Source of PTH
Chief cells in parathyroid
32
Functions of PTH (4)
1. Increases bone resorption of calcium and phosphate 2. increase kidney reabsorption of calcium in distal convoluted tubule 3. decrease reabsorption of phosphate in proximal convoluted tubule 4. increase 1alpha-hydroxylase activity in kidney (increases 1,25-(OH)2 D3 (calcitriol) Increased serum Calcium, decrease serum phosphate, and increase urine phosphate
33
Mechanism of bone resoprtion by PTH
Increases production of M-CSF and RANK-L in osteoblasts, which stimulates osteoclasts
34
What increases or decreases PTH secretion
Low calcium and magnesium stimulates PTH | Very low magnesium inhibits PTH
35
Common causes of low magnesium (4)
``` Diarrhea Aminoglycosides Diuretics Alcohol abuse Citrate (in whole blood or packed RBC transfusion) can chelate Ca2+/Mg2 ```
36
Function of vitamin D
Increase absorption of dietary calcium and phosphate | Decrease bone resorption of calcium and phosphate
37
Pathway of Vitamin D synthesis
From Skin: 7-dehydrocholesterol is converted to cholecalciferol (D3) or dietary intake of D2 from plates) Both converted to 25-OH in liver -> 1,25-(OH)2 in kidney
38
What is the active and inative forms of vitamin D
Active: 1,25-(OH)2 Inactive: 24,25-(OH)2
39
What regulates vitamin D?
Increased PTH | 1,25-(OH)2 feedback inhibits its own production
40
Source of calcitonin
C cells (parafollicular cells) of thyroid
41
Function of calcitonin
Decrease bone resoprtion of calcium | Opposes PTH, but not important in normal calcium homeostasis
42
Regulation of calcitonin
Increased serum Ca2+ causes calcitonin secretion.
43
What endocrine hormones signal through cAMP? (12)
[FLAT ChAMP] | FSH, LH, ACTH, TSH, CRH, hCG, ADH-V2, MSH, PTH, calcitonin, GHRH, glucagon
44
What endocrine hormones signal through cGMP? (2)
ANP, NO (EDRF)
45
What endocrine hormones signal through IP3?
[GGOAT] | GnRH, GHRH, Oxytocin, ADH-V1, TRH, histamine-H1, angiotensin II, gastrin
46
What endocrine hormones signal through steroid receptors?
[VETTT CAP] | Vitamin D, Estrogen, Testosterone, T3/T4, Cortisol, Aldosterone, Progesterone
47
What endocrine hormones signal through intrinsic tyrosine kinse? (MAPK pathway)
Insulin, IGF-1, FGF, PDGF, EGF
48
What endocrine hormones signal through receptor-associated tyrosine kinase? (JAK/STAT pathway)
[PIG] | Prolactin, Immunomodulators (cytokines, IL-2, IL-6, IL-8, IFN), GH
49
What happens if there is increased/decreased sex hormone-binding globulin in males and females?
(Increased SHBG) Decreased free testosterone -> gynecomastia (males) (Decreased SHBG) Increased free testosterone -> hirsutism in females SHBG levels increase during pregnancy
50
Source of T3/T4
Follicles of thyroid | Most T3 formed in target tissues
51
Functions of thyroid hormone (5)
1. Bone growth (synergistic with GH) 2. CNS maturation 3. increase beta-1 receptors in heart (increase CO, HR, SV, contractility) 4. increase basal metabolic rate through increased Na/K ATPase activity (increase O2 consumption, RR, body temperature) 5. increase glycogenolysis, gluconeogenesis, lipolysis
52
How does thyroid hormone increase heart rate, SV, and contractility in the heart?
Increased beta-1 receptors in heart
53
How does thyroid hormone increase basal metabolic rate?
Increase Na/K ATPase activity
54
What can increase or decrease TBG level?
Decreased: hepatic failure Increased: pregnancy, OCP (estrogen)
55
Function of peroxidase
Oxidation and organification of iodide | Coupling of MIT and DIT
56
Function of 5'-deiodinase
Converts T4 to T3 in peripheral tissue (T3 binds receptor with greater affinity)
57
Regulation of thyroid hormone
Negative feedback by free T3 to anterior pituitary decreases sensitivity to TRH
58
What is the Wolff-Chaikoff effect?
Excess iodine inhibits thyroid peroxidase -> decrease iodine organification -> decreases T3/T4
59
What inhibits iodine transport into follicular cells?
Anions (perchlorate, pertechnetate)
60
Functions of oxytocin
Uterine contraction during labor | Release of breast milk (let-down) in lactating mothers

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