Endocrine

Question 1

What are the major effects of prolactin?

Answer 1

Promotes milk secretion and maternal behavior

Question 2

Define lactotrope

Answer 2

Cells that synthesize prolactin

Question 3

What are the major effects of lutenizing hormone (LH)?

Answer 3

females: stimulates ovulation
males: stimulates testosterone secretion
- synthesized in gonadotrope cells

Question 4

What are the major effects of follicle stimulating hormone FSH?

Answer 4

females: stimulates ovarian follicle growth
males: stimulates spermatogenesis
- synthesized in ganadotrope cells

Question 5

What are the positive and negative feedback loops on Prolactin?

Answer 5

Positive:
-Breast suckling, TRH, VIP
-moderate levels of estrogen
Negative:
-Dopamine
-high levels of estrogen

Question 6

What are the positive and negative feedback loops acting on gonadotrope cells that produce LH and FSH?

Answer 6

positive:
-GNRH: gonadotropin releasing hormone
negative:
-estogen and testosterone from gonads

Question 7

What does hyperprolactinema often result from?

Answer 7

Prolactinoma-most common pituitary tumor.

Question 8

What are treatments for hyperprolactinemia?

Answer 8

-bromocriptine and cabergoline

dopamine agonists acting on D2 dopamine receptor of the lactotrope

Question 9

What are the major effects of ADH, anti diuretic hormone (aka vasopressin)?

Answer 9

Promotes renal water retention

Question 10

What is central diabetes insipidus due to?

Answer 10

Failure to secrete ADH

Question 11

What are the major effects of oxytocin?

Answer 11

-acts on breast to eject milk and on uterus to cause contractions

Question 12

What are the major effects of growth hormone on metabolism and stature?

Answer 12

metabolism:
-spares glucose utilization, increases availability of FFAs, promotes amino acid uptake and protein synthesis
-decreases adiposity and increases lean body mass
-diabetogenic b/c long term admin of growth hormone can make tissues resistant to effect of insulin
Growth:
-promotes limb and internal organ growth
-net linear bone growth at epiphyses

Question 13

What are insulin like growth factors IGFs? aka somatomedins

Answer 13

-have similar effects to insulin and mediate effects of growth hormone

Question 14

How does insulin induced hypoglycemia be used to test hypothalamic pituitary axis?

Answer 14

Insulin induced hypoglycemia–>following should happen:
ACTH increases–>cortisol
GH increases
oppose the action of insulin

Question 15

How do mutations in G proteins lead to tumors causing acromegaly or giantism and why are such tumors usually not malignant?

Answer 15

mutations in somatotroph G proteins lead to elevated levels of cAMP and hyper secretion of GH. If hyper secretion occurs in youth, results in giantism and if hyper secretion occurs after closure of epiphyses, leads to acromegaly. Not malignant because mutations retain differentiated functions and don’t metastasize.

Question 16

Why is IGF-1 and not hGH a candidate pharmaceutical to treat Laron syndrome?

Answer 16

Laron syndrome is due to resistance to GH b/c of mutations in GH receptor that prevents GH from acting. treatment of IGF-1 to restore growth.

Question 17

Why are calcium homeostasis and phosphate homeostasis linked?

Answer 17

99% of calcium is complexed with 85% of phosphate in the body to form hydroxyapatite in bone.

Question 18

Why do circulating Calcium levels need to be controlled?

Answer 18

hypocalcemia leads to life threatening tetanic contractions

hypercalcemia leads to impaired mentation and consciousness and muscle weakness

Question 19

How is the synthesis of 1,25(OH)2-VItD regulated?

Answer 19

• liver converts vitD3 to 25(OH)-VitD–>converted in kidney by 1-alpha-hydroxylase to 1,25(OH)2-VItD (active form)
• fall of calcium, estrogen, prolactin: increases PTH, acts on kidney, increases 1,25(OH)2-VItD to maintain levels
• negative feedback: on 1-alpha-hydroxylase, which leads to formation of less active metabolites 24,25(OH)2 and 1,24,25(OH)3

Question 20

What is the potential role of 1-alpha-hydroxylase in regulating immune response?

Answer 20

-TLR ligands and immune system cytokines may promote synthesis of 1,25(OH)2-VItD in macrophages, which promotes responses that help clear pathogens

Question 21

Why does a deficiency in Vit D lead to depressed levels of 25(OH) Vit D, normal levels of 1,25(OH)2-VItD, and elevated PTH levels?

Answer 21

Vit D deficiency leads lower 25(OH)Vit D and to compensatory elevation of PTH, which promotes conversion of 25(OH) Vit D to 1,25(OH)2-VItD.

Question 22

How is PTH synthesis and release regulated?

Answer 22

Plasma Ca2+ concentration is the principle regulator. As plasma Ca++ falls, PTH secretion increases.

Question 23

What are the major effects of PTH?

Answer 23

-act on bone to promote bone resorption and release of Ca and PO4 ions. PTH acts to increase phosphate and reduce calcium excretion in urine. Also increases formation of 1,25(OH)2-VItD in kidney, leading to increased Ca++ absorption in gut.