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Hypopituitarism

Clinical suspicion

Suspect hypopituitarism if there are manifestations suggestive of deficiency in more than one endocrine system.

The presence of CNS pressure manifestations is suggests that pituitary tumors are the cause. Local pressure manifestations include headache, visual field defects, optic atrophy, cranial nerve palsies, Korsakoff-like syndrome with recent memory loss (pressure on the 3rd ventricle) and hyperphagia or thirst sensations which may result from hypothalamic involvement.

Diagnosis

Once suspected a blood sample is drawn for hormonal analysis and hydrocortisone 100mg given once followed by 50mg 6 hours later and then regular replacement of the dose (20-30mg divided over two daily doses). This is done to avoid the risk of adrenal insufficiency or coma that may complicate the confirmatory tests.

1. Basal hormone levels of FSH, LH, GH, PRL, testosterone, oestradiol, progesterone, cortisol, thyroxine (T4) and tri-iodothyroxine (T3). It is of importance to note that the presence of normal gonadal function makes the presence of multiple pituitary defects unlikely.

2. Combined pituitary stimulation test:
A bolus of insulin (0.15 u/kg), GnRH (100 ug) and TSH (200 ug) is given intravenously and blood glucose, GH, FSH, LH, TSH and cortisol are serially measured for 2 hours. Levels below normal are characteristic of hypopituitarism.

3. CAT scan or MRI of the brain to exclude pituitary tumors.

Treatment

Long term replacement therapy and restoration of fertility. Steroids are replaced before thyroid hormones to avoid precipitating acute adrenal insufficiency by increasing the metabolic rate if thyroxine is given first.

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