Testing for Hypopituitarism
When there is a suspicion of hypopituitarism several endocrine tests will need to be done to document the loss of the hormone before treatment is instituted. For loss of TSH function, simply finding that the thyroid hormone levels (T4 and T3) and the TSH level are low is sufficient. Similarly, for loss of LH and FSH, finding these hormones low along with low estrogen levels in women or testosterone levels in men will suffice. In addition, a sperm count in men may also be helpful. Documenting ACTH deficiency usually requires a stimulation test because it is the response of ACTH and the adrenal hormone cortisol to stress that is really the important aspect of ACTH secretion. Thus, stimulation of ACTH and cortisol secretion by making a person have a low blood sugar level (hypoglycemia) by giving a small amount of insulin (insulin tolerance test) is a common type of test. Another involves blocking the amount of cortisol secreted using a compound called metyrapone. Sometimes tests involving stimulating the adrenal gland with ACTH (Cortrosyn test) or both the pituitary and the adrenal with the hypothalamic hormone corticotropin-releasing hormone (CRH test) are done. For GH, the insulin tolerance test also works very well but other tests that might stimulate GH secretion, such as exercise, a medication called L-dopa, or an amino acid called arginine may also be used. In children assessment of bone maturation is usually also done by doing an x-ray of the hand and wrist.
