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Hypopituitarism - What tests are necessary?

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The tests needed to make a diagnosis depend on the patient’s symptoms, the type of pituitary problem and the type of treatment received ( surgery, radiation). In general, a patient with a large pituitary adenoma is more likely to have a hormone deficiency than a patient with a small adenoma. A single blood test to determine the pituitary and target organ hormone levels may be all that is needed.

Sometimes a stimulation test is necessary to determine if there is a hormone deficiency. This is particularly true when evaluating cortisol or GH deficiencies. In the first kind of stimulation test, the patient is administered a hormone such as synthetic ACTH (“Synacthen test”) and then adrenal function is assessed. For a GH stimulation test, GH-releasing hormone (with an amino acid, arginine) is injected in the vein and then GH levels are evaluated. A combined test to assess cortisol and GH deficiency involves giving the patient a small dose of intravenous insulin. Insulin causes a reduction in blood glucose, and the low glucose level itself increases both cortisol and GH levels. Stimulation tests must be conducted under careful medical supervision. Important: An insulin tolerance test should not be performed in elderly patients or patients with a history of heart disease, stroke or epilepsy.

Thyroid hormone deficiency is diagnosed by measuring the levels of TSH (pituitary hormone) and thyroid hormone (produced by the thyroid) in the blood. The level of thyroid hormone itself is the more important measurement for making the diagnosis.

In women, a diagnosis of LH and FSH deficiency is determined based on the menstrual history. Regular menstrual cycles in women not taking oral contraceptives usually means there is no deficiency. Women who are menopausal are expected to have elevated LH and FSH levels because their ovaries no longer work effectively; therefore, normal or low LH and FSH levels in menopausal women usually indicate a deficiency in one or both of these pituitary hormones.

In men, LH and FSH deficiencies are determined by asking about sex drive and ability to have erections and by measuring the LH, FSH and testosterone levels in the blood. If the testosterone level is below normal and LH and FSH levels are normal or low, hypopituitarism regarding sex hormones is confirmed. These men might also have noticed a reduction in the size of the testes, which may also be soft. For men who are concerned about fertility, a semen analysis (measures number of sperm and quality of sperm movement) is necessary.

Antidiuretic hormone deficiency (diabetes insipidus) is suggested on the basis of symptoms of increased thirst and an increased amount and frequency of urination, particularly at night. A 24-hour urine collection may be used to confirm output of large volumes of urine. Blood and urine tests are important for confirming the diagnosis. A high level of sodium in blood and low urine concentrating ability indicate a diagnosis of DI. Occasionally, to confirm a diagnosis of DI, the patient is hospitalized so a water deprivation test can be performed. The test involves withholding fluid and measuring blood sodium and osmolality over several hours. The time it takes to conduct the test depends on the severity of the DI.