Hypothalamus, Pituitary, Target Gland Axis & Growth Hormone

What is the role of the hypothalamus in endocrine control?

It monitors blood composition and releases releasing or inhibiting hormones that control the anterior pituitary.

How do hypothalamic hormones reach the anterior pituitary?

Through the hypophyseal portal system (2 capillary beds → direct control)

What type of hormones does the anterior pituitary produce?

Tropic hormones that stimulate other glands (TSH, ACTH, FSH, LH).

Which pituitary hormones are direct acting, not tropic?

GH (acts on body tissues) and Prolactin (PRL) (acts on mammary glands).

What stimulates GH release?

GHRH from hypothalamus → anterior pituitary → GH → bones & muscles.

What inhibits GH release?

GHIH (somatostatin) from hypothalamus.

What feedback controls GH levels?

Rising GH or IGF levels inhibit GHRH and stimulate GHIH → stops further GH release.

GH imbalance disorders?

• Gigantism → excess GH before puberty

• Dwarfism → too little GH before puberty

• Acromegaly → excess GH after puberty