Clinical Manifestations Of Hypofunction Of Pituitary Gland Disorders: Hypopituitarism
A General Overview
When there is failure of one or more cell types of the pituitary to secrete normally, hypopituitarism results. It is unusual to get deficiencies of single hormones. More often several hormones are deficient. The condition commonly presents as dwarfism in children and hypogonadism in adults. Hypopituitarism may result from different pathological processes.
- Removal of the gland by surgery or irradiation.
- Tumours of the pituitary, suprasella tumours or carcinomatous seconday deposits.
- Granulomatous diseases- Sarcoidosis, Hand-Schuller Christian disease, eosinophilic granuloma.
- Infiltrations- Leukemia, lymphoma.
- Infarction- Postpartum necrosis due to hemorrhage (Sheehan’s syndrome), diabetes, sickle cell disease, cavernous sinus thrombosis, temporal arteritis, carotid aneurysm.
- Infections- tuberculosis, syphilis
- Viperine snake bite- panhypopituitarism has been recorded in many cases, several years after recovery from viper bite.
Symptoms depend on the type and severity of cell failure, age of the patient and the age of onset of the disease. The condition becomes overt only when more than 75% of cells are destroyed. Gonadotropin, growth hormone, thyrotropin and ACTH are all reduced in different proportions. Hypoprolactinemia manifests only during the puerperium as failure of lactation.
Clinical features: One of the common modes of presentation is Sheehan’s syndrome in which the hyperplastic pituitary of pregnancy which is vulnerable for ischemic damage undergoes infarction due to postpartum hemorrhage and shock. The earliest manifestation is failure of lactation. The patient develops amenorrhea, genital atrophy, loss of axillary and pubic hair, and loss of libido. Men with hypopituitarism present with testicular atrophy, loss of libido and absence of spermatogenesis. Failure of ACTH leads to secondary adrenal cortical failure. As the hypopituitarism advances, thyroid hormone deficiency also manifests. It is rare to get classical myxedema. The reduction in growth hormone is not usually evident clinically. The symptoms of GH deficiency include lack of strength due to reduction in muscle mass, increased insulin sensitivity and mild refractory anemia.
Differential diagnosis: Panhypopituitarism has to be differentiated from other causes of dwarfism, general debility and asthenia. Anorexia nervosa which affects young women between the ages of 15 and 30 may mimic hypopituitarism. In anorexia nervosa, all the pituitary hormones except GH are decreased. With weight loss of more than 20% amenorrhea may also develop. Unlike hypopituitarism, the public and axillary hair are retained. Moreover, emaciation is more suggestive of anorexia nervosa.
Investigations And Management
The diagnosis of panhypopituitarism is established by estimating the pituitary hormones and the hormones of the target glands. Stimulation tests reveal the functional integrity of the target glands.
- ACTH secretion: When adrenal response to ACTH is established, metyrapone test or insulin hypoglycemia may be used to test the pituitary reserve of ACTH.
- TSH reserve: This can be easily assessed by administration of TRH. This could also elucidate the PRL secretory status of pituitary.
This consists of replacement of the hormones of the target organs. Cortisol deficiency is corrected with 12.5-25mg of cortiso or its equivalent of other synthetic steroids. Glucocorticoids should be replaced before supplementation of thyroxine and gonadotropins in order to avoid the development of adrenal crisis. Glucocorticoid replacement should be increased during periods of acute stress like operations and infections. Mineralocorticoid replacement is not usually needed since this hormone is not markedly deficient in hypopituitarism. Thyroid replacement is best achieved with synthetic thyroxine started in a dose of 50-100 ug/Kg and raised to a dose of 150- 200ug slowly.
Testosterone replacement improves vigour, vitality and libido. The oral preparation is methyl testosterone. Alternatively, testosterone can be given intramuscularly as depot injections. Estrogen and progesterone therapy prevent atrophy of the breasts and vaginal mucosa and osteroporosis.
Finally, Gonadotropin replacement is essential for return of ovulation and spermatogenesis. Short courses of a mixture of FSH and LH (menotropins) followed by human chorionic gonadotropins (HCG) are used to induce ovulation.
© 2014 Funom Theophilus Makama