Lecture 14- Hypothalmic Pituitary Axis And GH

Question 1

What is the hypothalamic pituitary axis?

Answer 1

Functional unit that acts as major link between endocrine and nervous system

Question 2

Posterior vs anterior pituitary anatomy?

Answer 2

Posterior is connected to hypothalamus through infundibulum or pituitary stalk and fed by inferior hypophysis artery.

The anterior pituitary is not directly connected to hypothalamus. Hormones released and stored in Median eminence before being released into hypophysis portal system and travel to anterior pituitary.

Question 3

Important difference between anterior and posterior?

Answer 3

Hormones from posterior pituitary come from hypothalamus and enter blood and have endocrine function. Hormones in posterior pathway released into hypophyseal portal system which then act in anterior endocrine tissue and stimulate the release of other hormones into blood which can have endocrine function

Question 4

What is a hormone that controls the release of another hormone called?

Answer 4

A tropic hormone

Question 5

What are the six tropic hormones produced by the hypothalamus that act on the anterior pituitary?

Answer 5

TRH or thyrotropin releasing hormone

Prolactin release inhibiting hormone (dopamine)

CRH corticotropin releasing hormone

GnRH gonadotropin releasing hormone

GHRH Growth hormone releasing hormone

GHIH growth hormone inhibiting hormone (somatostatin)

Question 6

Hormones produced by anterior pituitary?

Answer 6

TSH

ACTH

LH

FSH

PRL

GH

Question 7

Negative feedback in hormone control of GH?

Answer 7

GH and IGF will inhibit GHRH and stimulate release of somatostatin.

Also inhibit GH release

GH will also inhibit GHRH

Question 8

How does growth hormone exert its effects?

Answer 8

Through promoting the release of IGFs

Question 9

What can alter GHRH secretion?

Answer 9

Increased by Deep sleep, stress, fasting, exercise

Inhibited by obesity, REM sleep,

Question 10

GH deficiency?

Answer 10

In children results in pituitary dwarfism
Bottom 3 percentile for height
Treated with GH therapy

Question 11

GH excess?

Answer 11

Lead to gigantism which can progress to acromegaly in adults

Question 12

What IGF types are there?

Answer 12

IGF1 major growth factor in adults and IGF2 which is the major growth factor in fetal growth

Question 13

What other hormones influence growth?

Answer 13

Insulin and thyroid hormone are two examples