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Post Surgery Testing for Pituitary Hormones

Question: After pituitary surgery, in addition to cortisol and ACTH, what other pituitary hormone levels should be checked and when?  

Answer: Following pituitary surgery, there is always the possibility of other hormone deficiencies, depending on how much of the pituitary was removed. Other hormone replacements may include thyroid hormone, estrogen and progesterone in pre-menopausal women and growth hormone. In patients with diabetes insipidus, desmopressin (DDAVP) is needed to prevent excessive urination and thirst. Regarding estrogen and progesterone replacement, it is best to wait 3 or 4 months after pituitary surgery to see if menstrual cycles return.

Regarding thyroid hormone replacement, a blood test for thyroid hormone (Free T4, not just a TSH) measured 6 to 8 weeks after surgery is needed to determine if thyroid hormone is required. Thyroid hormone is a hormone necessary for life; it regulates the body’s metabolism. Symptoms of thyroid deficiency include fatigue, weight gain, and difficulty with memory. Diagnosis of thyroid hormone deficiency is straightforward with blood tests to measure free T4 (secreted by the thyroid gland) and TSH (secreted by the pituitary to stimulate the thyroid gland). The free T4 level is the most reliable in a patient who has had pituitary surgery. Thyroid hormone deficiency is not common if the normal pituitary has not been removed.

Growth hormone (GH) deficiency may require a special stimulation test such as an arginine or insulin test (most insurance carriers require documentation of growth hormone deficiency with the results of a stimulation test). Growth hormone, affects body composition (increases muscle mass, decreases fat mass, increases bone mass, it does not cause weight loss). It may also improve blood cholesterol levels and improve energy and exercise ability. GH is not an “anti-aging” hormone. GH deficiency after pituitary surgery depends on the amount of normal pituitary gland removed. If the normal pituitary gland was left intact after the operation, GH deficiency should not be a problem. Again, the diagnosis of GH deficiency usually requires a stimulation test. Patients who have had pituitary surgery that required removal of normal pituitary tissue should be tested for GH deficiency.

At our clinic, eight weeks after pituitary surgery, we measure the IGF-1 homone. If it is low or the patient has symptoms of growth hormone deficiency, a stimulation test is performed (usually an insulin hypoglycemia test) to diagnose growth hormone deficiency. If a patient has had radiation treatment to the pituitary, we measure IGF-1 once or twice a year and if it becomes low, then perform a stimulation test.

The important thing to know is that with appropriate hormone replacement(s), a person can live a normal life. Although “Mother Nature” does it best, current hormone treatments can be almost as good as Mother Nature. This may require adjustment of medications over time. Although very few get “tailor made suits” these days – hormone replacement is like a tailor made suit – it must be adjusted to every patient’s individual needs. It is important for the patient to see her/his Endocrinologist regularly to assess response to treatment and blood tests. In patients who had an adrenal operation, there should be no need for thyroid hormone, estrogen and progesterone or growth hormone replacement – the normal pituitary gland was not disturbed.

By Dr. Mary Lee Vance (Winter, 2013)

 

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