Hypopituitarism
Hypopituitarism, also known as panhypopituitarism, is a complex syndrome marked by metabolic dysfunction, sexual immaturity, and growth retardation (when it occurs in childhood), resulting from a deficiency of the hormones secreted by the anterior pituitary gland. Panhypopituitarism refers to a generalized condition caused by partial or total failure of all six of this gland’s vital hormones—corticotropin, thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), human growth hormone (hGH), and prolactin. Partial hypopituitarism and complete hypopituitarism occur in adults and children; in children, these diseases may cause dwarfism and delayed puberty. The prognosis may be good with adequate replacement therapy and correction of the underlying causes.
Causes
The most common cause of primary hypopituitarism is a tumor. Other causes include congenital defects (hypoplasia or aplasia of the pituitary gland); pituitary infarction (most commonly from postpartum hemorrhage); partial or total hypophysectomy by surgery, irradiation, or chemical agents; and, rarely, granulomatous disease (tuberculosis, for example). Occasionally, hypopituitarism may have no identifiable cause, or it may be related to autoimmune destruction of the gland. Secondary hypopituitarism stems from a deficiency of releasing hormones produced by the hypothalamus—either idiopathic or possibly resulting from infection, trauma, or a tumor.
Primary hypopituitarism usually develops in a predictable pattern of hormonal failures. It generally starts with hypogonadism from gonadotropin failure (decreased FSH and LH levels). In adults, it causes cessation of menses in women and impotence in men. hGH deficiency follows; in children, this causes short stature, delayed growth, and delayed puberty. Subsequent failure of thyrotropin (decreased TSH levels) causes hypothyroidism; finally,
adrenocortical failure (decreased corticotropin levels) results in adrenal insufficiency. When hypopituitarism follows surgical ablation or trauma, the pattern of hormonal events may not necessarily follow this sequence.
adrenocortical failure (decreased corticotropin levels) results in adrenal insufficiency. When hypopituitarism follows surgical ablation or trauma, the pattern of hormonal events may not necessarily follow this sequence.
Sometimes, damage to the hypothalamus or neurohypophysis from one of the above leads to diabetes insipidus.
Signs and symptoms
Clinical features of hypopituitarism develop slowly and vary with the severity of the disorder and the number of deficient hormones. Signs and symptoms of hypopituitarism in adults may include gonadal failure (secondary amenorrhea, impotence, infertility, and decreased libido), diabetes insipidus, hypothyroidism (fatigue, lethargy, sensitivity to cold, and menstrual disturbances), and adrenocortical insufficiency (hypoglycemia, anorexia, nausea, abdominal pain, and orthostatic hypotension).
Postpartum necrosis of the pituitary (Sheehan’s syndrome) characteristically causes failure of lactation, menstruation, and growth of pubic and axillary hair as well as symptoms of thyroid and adrenocortical failure.
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