Question

Because Growth Hormone _______, inhibition involves a(n) _________.

A. is a tropic hormone ; negative feed-back-loop

B. acts on an endocrine gland ; positive feed-back loop

C. is not a tropic hormone ; Inhibitory Hormone (IH)

D. is not a tropic hormone ; negative feed-back loop

E. is a Releasing Hormone ; negative feed-back loop

Answer 1

Option D is correct.

Growth hormone is NOT a tropic hormone and it's inhibition involves a NEGATIVE LOOP feedback mechanism.

Tropic hormone are those which after being secrected from an endocrine gland acts on another endocrine gland either to enhance or inhibit release of other hormone. But,although get secreted from anterior pituitary, Growth hormone doesn't act on other endocrine gland. Instead, it acts on hepatocyte,adipocyte etc. to carry out it's direct and indirect actions. So,Growth hormone is neither a tropic hormone nor a releasing hormone.

Secretion of Growth Hormone (GH) involves Negative feedback loop mechanism. Increased blood levels of GH inhibits secretion of Growth hormone releasing hormone( GHRH) from hypothalamus which in turn inhibits the release of GH from somatotroph of anterior pituitary. Increased levels of Insulin like Growth factor (IGF-I) also suppress somatotrophs.