Question: I had a pituitary tumor removed and am no longer on replacement medication. It seems that even something minor, like a cold, causes havoc with my system, including aches and pains. Is this normal after having had Cushing’s?
Answer: Following the removal of an ACTH secreting pituitary tumor (or an adrenal cortisol secreting tumor), it takes on average 1 year before the pituitary-adrenal axis begins producing normal levels of cortisol. This occurs because the long term overproduction of cortisol has put to rest the normal ACTH producing pituitary cells that were not part of the pituitary tumor. Patients absolutely need to take cortisone replacement during this time period. In addition supplemental cortisone replacement (up to 2-3 times the normal amount) needs to be taken in case of a serious stress or illness. The relative lack of cortisol can manifest itself with fatigue, diffuse muscular and joint pains, lack of appetite, abdominal pain, low blood pressure or shock.
Once this axis recovers its basal level production of cortisol (measured by the determination of morning plasma cortisol prior to taking the replacement dose), it is then necessary to determine whether the pituitary and adrenal glands can produce sufficient amounts of cortisol during stress, such as an illness. To verify this, the patient is tested with an intravenous injection of ACTH (a synthetic form called Cortrosyn) to determine whether the adrenal reserve to produce increased cortisol is back to normal. In specific circumstances, it may be indicated to test the pituitary reserve in ACTH by injecting insulin intravenously under carefully controlled guidelines, to induce hypoglycemia, commonly called low blood sugar. The body perceives this as a stressful situation and should increase ACTH and cortisol production, as measured by plasma cortisol levels.
It is also possible that patients who have undergone pituitary surgery could have relative deficiencies of other hormones, such as TSH (which normally regulates thyroid hormone levels), growth hormone, prolactin (regulates milk production), FSH and LH (which regulate ovarian and testicular function) or vasopressin (which regulates urine volume). These hormones can be assessed during pituitary reserve tests where in addition to insulin induced hypoglycemia, stimulation with TRH and LHRH is performed. These hormones should be replaced (with the exception of prolactin) if they are found to be deficient.
By Dr. Andre Lacroix MD (Fall, 1997)