THE endocrine glands are components of feedback loops whose function is to control the concentration of substances in the circulation.¹ These substances may be hormonal (e.g., thyroxine) or nonhormonal (e.g., glucose). Disorders of endocrine loops may arise in two ways. Either efficiency is lost through destruction or atrophy, or there is hypersecretion of one of the components as a result of autonomy or nonphysiologic stimulation. Circulating concentrations of the substance being controlled may rise or fall, but in either case the capacity to impose constraint is lost and disease results. The endocrine glands are particularly susceptible to autoimmunity, which may . . .