Functional causes of pituitary insufficiency
It is important to exclude functional hypopituitarism when patients present with an isolated pituitary deficit. Patients receiving high doses of oral glucocorticoids for > 6 weeks or those having frequent articular or epidural glucocorticoid injections or using high doses of potent inhaled glucocorticoids have suppressed plasma ACTH levels and may develop transient adrenal atrophy. Depending on dosing and length of exposure to glucocorticoids, these patients may or may not exhibit cushingoid features. Body builders withdrawing from anabolic–androgenic steroids can exhibit undetectable LH and FSH and very low testosterone levels in conjunction with polycythemia. Hypothalamic amenorrhea, characterized by low serum levels of estradiol, LH, and FSH, can be caused by anorexia nervosa, strenuous exercise, and high levels of stress. Hyperprolactinemia also suppresses secretion of LH, FSH, and gonadal steroids; decreased testosterone or estrogen concentrations usually normalize after correcting hyperprolactinemia with dopamine agonists. Critical illness and high-dose opioids may suppress both the hypothalamic–pituitary–adrenal and the hypothalamic–pituitary–gonadal axes.