hypopituitarism

Hypopituitarism is a disorder characterized by reduced secretion of one or more hormones produced by the anterior pituitary gland (adenohypophysis) or, less commonly, disruption of posterior pituitary function. Because the pituitary coordinates several endocrine axes, hypopituitarism can cause multiple hormone deficiencies. It can be partial or complete and may involve a single hormone or multiple axes.

Common causes include pituitary adenomas (especially nonfunctioning tumors), pituitary infarction after childbirth (Sheehan syndrome), cranial irradiation, head trauma, infiltrative diseases such as hemochromatosis, infections, and congenital pituitary or hypothalamic developmental abnormalities. Less frequent causes include inflammatory disorders, vascular malformations, and genetic mutations affecting pituitary development or function.

Clinical features depend on which hormones are affected. Growth hormone deficiency in children presents with short stature and delayed growth; gonadotropin deficiency causes delayed or absent puberty; ACTH deficiency leads to secondary adrenal insufficiency with fatigue, anorexia, abdominal pain, and hypotension; TSH deficiency causes central hypothyroidism, with fatigue and cold intolerance. In adults, symptoms may include fatigue, reduced libido, weight changes, and weakness. Diagnosis involves assessing pituitary and target-hormone levels, followed by dynamic testing (eg, ACTH stimulation, cortisol response; insulin tolerance test) if needed, and magnetic resonance imaging to evaluate the pituitary and nearby structures.

Treatment focuses on hormone replacement for deficient axes and addressing the underlying cause when possible. Glucocorticoids are required for ACTH deficiency and must be in place before initiating thyroid hormone. Levothyroxine treats central hypothyroidism. Growth hormone therapy is used for confirmed pediatric (and selected adult) deficiency. Sex hormone replacement may be considered for gonadotropic deficiency. Regular monitoring for responses and adverse effects is essential.