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PITUITARY INSUFFICIENCY

Panhypopituitarism is a rare congenital problem. Pituitary insufficiency is usually seen later in life as a consequence of pituitary gland destruction caused by an enlarging macroadenoma, or surgical or radiation treatment of an adenoma. Microadenomas, on the other hand, rarely cause significant pituitary destruction, but can result in overproduction of selected anterior pituitary hormones, especially prolactin. Also, individuals may develop pituitary insufficiency after ischemia, as seen in shock and birth asphyxia. Rarer causes of pituitary insufficiency include infiltrative diseases.

Congenital hypopituitarism should be suspected in newborns with unrelenting jaundice or unexplained hypoglycemia. The cause of hyperbilirubinemia remains controversial. Hypoglycemia develops.

Frequent bottle feedings may mask the hypoglycemia, a situation that may happen in nurseries. As feeding frequency decreases or while the maternal milk supply is establishing itself, newborns can develop prolonged and severe hypoglycemia. Another finding of congenital panhypopituitarism is micropenis because gonadotropins are required.

Causes of Pituitary Insufficiency

Childhood

Congenital absence of the pituitary (empty sella syndrome)

Genetic disorders (often associated with other endocrine deficiencies)

Craniofacial tumors

Perinatal ischemia

Adulthood

Pituitary adenomas

Surgery or radiation therapy for pituitary

abnormality Ischemia or shock and pituitary necrosis

(Sheehan's syndrome)

Hemochromatosis

Histiocytosis

Granulomatous diseases

Features of Pituitary Insufficiency

Hormone deficiency Signs and symptoms/laboratory findings

Corticotropin Acute deficiency: fatigue, weakness,

nausea, vomiting, hypotension

Chronic deficiency: fatigue, pallor,

weight loss

Children: growth retardation

Laboratory findings: hyponatremia,

hypoglycemia

Thyroid-stimulating Adults: weight gain, fatigue, depression,

hormone mental status changes, dry skin, hair loss

Children: growth retardation, delayed

intellectual development, mental

retardation if untreated

Laboratory finding: hyponatremia

Gonadotropins Women: amenorrhea, infertility,

anovulation, loss of libido,

osteoporosis, premature atherosclerosis

Men: loss of libido, impaired sexual

function, decreased muscle mass,

hair growth

Children: micropenis, delayed puberty

Growth hormone Adults: decreased muscle mass and

strength, central obesity, fatigue,

premature atherosclerosis

Children: growth retardation

Laboratory finding: hypoglycemia

Prolactin None

Melanocyte-stimulating None

Treatment of pituitary insufficiency focuses on replacing hormones affecting the target organs of pituitary hormones, rather than the missing pituitary hormones. The most crucial hormones that must be replaced are the corticosteroids.

In most individuals, cortisol is dosed three times per day, with half the daily dose given in the morning and the remaining half split into afternoon and evening doses. This schedule produces a more physiologic response, with a morning peak.

Hormone Therapy for Pituitary Insufficiency

Deficiency Replacement recommendations

Corticotropin Adults: cortisone acetate (25.0 mg in a.m. and 12.5 mg in p.m.) or

prednisone (4.0 to 7.5 mg per day) or hydrocortisone (20 mg in a.m. and

I 0 mg in p.m.) or dexamethasone (Decadron^®, Hexadrol^®) (0.25 to 0.5

mg per day)

Children: cortisone acetate or hydrocortisone, 0.5 to 0.75 mg per kg per

day given as two or three divided doses

Crises: hydrocortisone, 100 to150 mg per day in adults and 30 to 60 mg

per m^~ per day in children

Thyroid stimulating hormone Adults: thyroxine (I 00 to 150 mcg per day, start at 25 to 50 mcg per day

in patients with risk of ischemic heart disease and increase slowly over

six to eight weeks); adjust according to free T₃ or free T₄ levels

Children: thyroxine (8 to I 0 mcg per kg per day); adjust according to

free T₃ or free T₄ levels assessed every three months

Gonadotropins (FSH/LH) Premenopausal women:

No fertility desired: cyclic estrogen/progesterone as in oral contraceptives

Fertility desired: cyclic human menopausal gonadotropin (hMG) with

human chorionic gonadotropin (hCG) to induce ovulation

Postmenopausal women: estrogen, e.g., conjugated estrogen

(0.625 mg per day) with medroxyprogesterone (5 mg per day),

(Premphase^®, Prempro^®) for women with an intact uterus