For hormones that homeostatically regulate cellular functions,
A) the circulating level of a hormone is held constant through a series of positive feedback loops.
B) endocrine organs release their contents into the bloodstream via specialized ducts.
C) it is impossible to also have neural regulation of that system.
D) negative feedback typically regulates hormone secretion.
E) both lipid-soluble hormones and water-soluble hormones bind to intracellular protein receptors.
Answer: D