With regards to circadian rhythms,

Correct Answer: D

Rationale: The suprachiasmatic nucleus (SCN) generates circadian rhythms via clock proteins.

Correct Answer: C

Rationale: These hormones travel via the portal system to regulate anterior pituitary secretion.

Correct Answer: D

Rationale: GH enhances amino acid uptake and lipolysis.

Correct Answer: C

Rationale: Tropic hormone deficiency causes secondary, not primary, hyposecretion.

Correct Answer: D

Rationale: Glucagon stimulates somatostatin secretion from D cells. It also increases insulin secretion, somatostatin inhibits it, diazoxide inhibits it, and K^+ depletion reduces it.