Pituitary Hormone Function

Question 1

The cells that secrete PRL, lactotrophs, comprise _____ of the adenohypophysis

Answer 1

30%

Question 2

high levels of prolactin inhibit pulsatile secretion of _______ by hypothalamic neurons

Answer 2

GnRH

Question 3

________ is released in both males and females in

response to stress

Answer 3

prolactin

Question 4

Prolactin interacts with specific receptors found in the _____

Answer 4

breast, liver,

ovary, testis and prostate

Question 5

prolactin, Upon ligand binding, receptors dimerize, leading to the activation of the _____ pathway

Answer 5

JAK/STAT

Question 6

Secretion of GH is under the influence of the hypothalamic hormones _____

Answer 6

GHRH and

somatostatin

Question 7

what is the direct effect of GH on muscle

Answer 7

Amino acid transport into the muscle is increased, and protein synthesis is increased.

Question 8

what are Direct actions of GH on adipose tissue?-

Answer 8

The net effect is to increase lipolysis and lead to mobilization of lipid and thus an increase in plasma free fatty acids (FFAs). Eventually, the effect of
GH on fat metabolism will be evidenced by a loss in subcutaneous fat. In this action GH antagonizes the action of insulin.

Question 9

what are the direct effects of GH on the Liver

Answer 9

Increased RNA, protein and glucose synthesis (through gluconeogenesis).
IGF-I will be secreted, which mediates the indirect effects.

Question 10

IGF receptors belong to the EGF/ Insulin receptor

family. Describe These receptors

Answer 10

These receptors contain an inherent tyrosine kinase activity and upon ligand binding can readily phosphorylate themselves (auto phosphorylation) and other proteins of the signal transduction pathway

Question 11

The major pathway activated by IGF receptors is
initiated by the binding of Insulin Receptor Associated proteins 1 and 2 (IRS I&II). IRS
in turn can bind to other molecules to activate either _______ or ________

Answer 11

the MAP kinase pathway,

transduction mediated by PI-3 kinase.

Question 12

what are the GH actions on bone/ cartilage mediated via IGF-I

iii. Adipose tissue - stimulates uptake of glucose and inhibits lipolysis. This
action of IGF is insulin like and antagonizes that of GH.

Answer 12

i. Bone/cartilage - Long bone growth is promoted by the stimulated proliferation
of epiphyseal cartilage. After puberty, the epiphyses seal and IGF-I no longer has this
effect on linear growth.

Question 13

what are the GH actions on Muscle mediated via IGF-I

Answer 13

stimulates proliferation, differentiation and protein synthesis

Question 14

what are the GH actions on adipose tissue mediated via IGF-I

Answer 14

stimulates uptake of glucose and inhibits lipolysis. This

action of IGF is insulin like and antagonizes that of GH.

Question 15

what factors inhibit GH secretion

Answer 15

hyperglycemia, 
high free fatty acid levels, 
obesity, 
α-adrenergic antagonists,
β-adrenergic agonists,
pharmacological doses of corticosteroids

Question 16

what factors stimulate GH secretion

Answer 16

hypoglycemia, 
amino acids (arginine), 
low free fatty acid levels, 
α-adrenergic agonists (clonidine), 
β-adrenergic antagonists (propranolol),
estrogens