Pituitary Hormone Function

Question 1

GH and PRL class of hormones

Answer 1

the somatomammotropin family, along with placental lactogen. -Polypeptides -share similarties in primary sequence.

Question 2

Regulation of PRL secretion

Answer 2

the hypothalamus tonically inhibits the secretion of PRL via PIH, or DA. Larger secretion if hypothalamic regulation is absent

Question 3

cells secreting PRL and its target

Answer 3

lactotrophs secret PRL. Target: The breast (mammary gland) is the principal target of PRL action

Question 4

PRL function

Answer 4

plays a role in the production of milk

Question 5

T or F: high levels of prolactin inhibit pulsatile secretion of GnRH by hypothalamic neurons

Answer 5

True, In cases where there are prolactin-secreting tumors, there will be inappropriate milk secretion & Reproduction is impaired.

Question 6

Stimulus for PRL secretion

Answer 6

-Suckling of breast in females -Stress in males & females

Question 7

Prolactin receptors

Answer 7

Members of the growth hormone/cytokine receptor families - Upon ligand binding, receptors dimerize, leading to the activation of the JAK/STAT pathway -well stimulated by GH

Question 8

Roles of GH

Answer 8

-fundamental for postnatal growth, -stimulates somatic growth and -regulates metabolism.

Question 9

T or F: 10% of the dry weight of the anterior pituitary is contributed by PRL

Answer 9

False, GH contribues 10% not PRL

Question 10

Regulators of GH secretion

Answer 10

under the influence of the hypothalamic hormones: 1. GHRH (increase cAMP) 2.somatostatin (decrease cAMP in somatotrophs)

Question 11

GH half life

Answer 11

The majority of GH circulates in an unbound form and has a half-life of 20-45 mi

Question 12

GH signaling

Answer 12

similiar to PRL , uses JAK/STAT pathway

Question 13

What is IGF-I

Answer 13

IGF-I is structurally related to proinsulin and has many insulin like actions - powerful mitogen and growth-promoting agent

Question 14

IGF receptors

Answer 14

belong to the EGF/ Insulin receptor family -inherent tyrosine kinase activity -activates Insulin Receptor Associated proteins 1 and 2 (IRS I&II). -IRS can bind to other molecules to activate either the MAP kinase pathway or transduction mediated by PI-3 kinase

Question 15

IGF actions

Answer 15

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. ii. Muscle - stimulates proliferation, differentiation and protein synthesis iii. Adipose tissue - stimulates uptake of glucose and inhibits lipolysis.

Question 16

Stimulus for GH release

Answer 16

-stress -Circadian Control (Increase during Sleep Stages 3&4) -GHRH -hypoglycemia, amino acids (arginine),low free fatty acid levels, -α- adrenergic agonists (clonidine), -adrenergic antagonists (propranolol) and estrogens. Review BRS CHart

Question 17

Inhibitors of GH release

Answer 17

-Somatostatin -hyperglycemia, high free fatty acid levels, obesity, α-adrenergic antagonists, β-adrenergic agonists as well as pharmacological doses of corticosteroids -Review BRS Chart

Question 18

Regulation of GH (BRS CHart)

Answer 18

Question 19

Regulation of PRL (BRS CHart)

Answer 19