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PITUITARY ANTERIOR LOBE DEFICIENCY IN ADULTS

PITUITARY ANTERIOR LOBE DEFICIENCY IN ADULTS

Anterior pituitary deficiency is decreased secretion of pituitary hormones caused by a disorder of the pituitary or hypothalamus. Compression of a normal pituitary gland by a pituitary adenoma is the most common cause. Other causes of anterior pituitary failure include pituitary cyst, pituitary surgery, pituitary radiation, infiltrative lesion (e.g., lymphocytic hypophysitis, hemochromatosis), infarction (e.g., Sheehan syndrome), apoplexy, genetic disorder (e.g., pit-1 mutation, POU1F1 mutation), primary empty sella syndrome, and metastatic disease to the sella. Hypothalamic diseases that may cause varying degrees of hypopituitarism include mass lesions (e.g., craniopharyngioma, germinoma, metastatic disease), radiation (e.g., for brain or nasopharyngeal malignancies), infiltrative lesions (e.g., sarcoidosis, Langerhans cell histiocytosis), trauma with skull base fracture, and infection (e.g., viral encephalitis, tuberculous meningitis).

The signs and symptoms related to anterior pituitary insufficiency may occur slowly or suddenly; may be mild or severe; and may affect the secretion of a single, several, or all pituitary hormones. Whereas pituitary apoplexy (see Plate 1-18) is an example of a sudden onset presentation dominated by abrupt loss of corticotropin (adrenocorticotropic hormone [ACTH]) secretion, the impact of slow-growing nonfunctioning pituitary adenomas or radiation therapy on pituitary function develops over years. Panhypopituitarism is the term used to describe deficiency of all pituitary hormones. Partial hypopituitarism is more common. In general, the secretion of growth hormone (GH) and gonadotropins is more likely to be affected than ACTH and thyrotropin (thyroid-stimulating hormone [TSH]). The clinical picture may be dominated by secondary hypogonadism from gonadotropin deficiency. With longstanding gonadal steroid deficiency, individuals develop fine facial wrinkles around the eyes, mouth, and cheeks. Pallor, out of proportion to the moderate anemia usually present, is observed. There is loss of axillary and pubic hair. In women, amenorrhea, infertility, vaginal dryness and atrophy, hot flashes, breast atrophy, osteoporosis, and loss of libido occur. In men, secondary gonadal failure may cause infertility, decreased libido, decreased vitality, decreased testicular size, erectile dysfunction, and osteoporosis.

PITUITARY ANTERIOR LOBE DEFICIENCY IN ADULTS


GH deficiency in adults may be associated with decreased sense of well-being, increased fat mass, decreased muscle mass, increased risk of cardiovascular disease, and decreased bone mineral density.

Prolactin deficiency may result in the inability to lactate postpartum.

Thyroid deficiency produces a subnormal temperature, cold intolerance, a low metabolic rate, fatigue, dry skin, periorbital puffiness (myxedema facies), bradycardia, anemia, delayed relaxation phase of the deep tendon reflexes, and constipation (see Plates 2-14 and 2-15). Also, the combined decrease of thyroid hormone and testosterone may result in loss of the lateral third of the eyebrows.

Adrenal insufficiency is responsible for low blood pressure, asthenia, weight loss, eosinophilia, and crises of nausea and vomiting, which may be associated with spontaneous hypoglycemia. Because the adrenal secretion of aldosterone is preserved, secondary adrenal failure does not cause salt wasting or hyperkalemia (see Plate 3-24). Also, the hyperpigmentation characteristic of primary adrenal failure (see Plate 3-22) is absent. However, both primary and secondary adrenal failure may cause hyponatremia, a result of inappropriate secretion of antidiuretic hormone (ADH; vasopressin) and a lack of permissive effect of cortisol for the kidneys to excrete free water.