Pituitary failure

Pituitary failure (secondary hypothyroidism) is an uncommon cause resulting from pituitary tumors, surgical therapy, external pituitary radiation, postpartum pituitary necrosis, metastatic tumors, tuberculosis, histiocytosis, and autoimmune mechanisms. 

Most patients with pituitary failure (secondary hypothyroidism) have clinical signs of generalized pituitary insufficiency such as abnormal menses and decreased libido, or evidence of a pituitary adenoma such as visual field defects, galactorrhea, or acromegaloid features. 

Pituitary failure (secondary hypothyroidism) should be suspected in a patient with decreased levels of T4 and inappropriately normal or low TSH levels. 

In patients with hypothyroidism caused by hypothalamic or pituitary failure, alleviation of the clinical syndrome and restoration of serum T4 to the normal range are the only criteria available for estimating the appropriate replacement dose of levothyroxine. 

Clomiphene is used in the treatment of disorders of ovulation in patients who wish to become pregnant. Usually, a single ovulation is induced by a single course of therapy, and the patient must be treated repeatedly until pregnancy is achieved, since normal ovulatory function does not usually resume. The compound is of no value in patients with ovarian or pituitary failure. 

The most serious adverse effect of protirelin is pituitary apoplexy (pituitary hemorrhage or infarction, characterized by severe headache, visual loss, and often by pituitary failure, hypotension, and coma). This complication has been described in 15 cases after pituitary function testing... 

A 72-year-old man taking metformin 1 g bd for type 2 diabetes began to have episodes of hypoglycemia, which resolved on stopping the metformin he also had anterior pituitary failure (46). 

Newey PJ, Abousleiman Y, Jamieson A. Pituitary failure, metformin and hypoglycaemia in type 2 diabetes. Br J Diabetes Vase Dis 2004 4 128-30. 

When puberty is delayed in a girl, measurement of serum gonadotropins is useful for diagnostic purposes. Low concentrations may indicate pituitary failure, whereas concentrations elevated mto the postmenopausal interval mdicate definite gonadal failure. In the latter case, chromosome studies are indicated. In the former case, pituitary function testing and radiography may be helpful. Patients... 

Hypothalamic dysfunction (Kallmann s syndrome) Pituitary failure (tumor, radiation, surgery) Hyperprolactinemia (drug, tumor)... 

TSH is required for normal thyroid secretion. Thyroid atrophy and decreased thyroid secretion follow pituitary failure. Pituitary insufficiency may be caused by destruction of thyrotrophs by either functioning or nonfunctioning pituitary tumors, surgical therapy, external pituitary radiation, postpartum pituitary necrosis (Sheehan s syndrome), infiltrative processes of the pituitary such as metastatic tumors, tuberculosis, histiocytosis, and autoimmune mechanisms. In all these sitnations, TSH deficiency most often occurs in association with other pituitary hormone deficiencies. 

Note that pituitary enlargement in hypothyroidism does not invariably indicate the presence of a primary pituitary tumor. Pituitary enlargement is seen in patients with severe primary hypothyroidism owing to compensatory hyperplasia and hypertrophy of the thyrotrophs. Serum TSH concentrations and pituitary enlargement decline during thyroid hormone replacement therapy, indicating that the TSH secretion is not autonomous. These patients are easily separated from patients with primary pituitary failure by measuring a TSH level. 

In patients with hypothyroidism caused by hypothalamic or pituitary failure, alleviation of the chnical syndrome and restoration of serum T4 to the normal range are the only criteria available for estimating the appropriate replacement dose of levothyroxine. Concurrent use of dopamine, dopaminergic agents (bromocriptine), somatostatin or somatostatin analogs (octreotide), and corticosteroids suppresses TSH concentrations and may confound the interpretation of this monitoring parameter. ... 

Growth hormone deficiency may be present from birth or due to later pituitary-failure. A variety of stimulation tests have been used to evaluate GH deficiency. Seram GH concentrations rise in response to exercise, and this may be u.sed as a preliminary screening test. They also rise during sleep, and high concentrations in a nocturnal sample may exclude GH deficiency. The lack of GH response to clonidine, a potent stimulant of GH secretion, isdiagnostic. Some centres have now abandoned the use of insulin-induced hypoglycaemia as a diagnostic test in children because of its hazards. 

Addison s disease is a rare, potentially fatal condition due to insufficient production of both aldosterone and cortisol caused by atrophy of the adrenal glands. It is characterised by low blood pressure, loss of sodium, weight loss and pigmentation of mucosal membranes. Adrenocortical insufficiency also results from pituitary failure with loss of adrenocorticotrophic hormone (ACTH) production. 

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