From Lewis S Blevins, Jr., M.D. – Today on Dr. Blevins’ Corner: An elderly man underwent removal of the thyroid gland many years ago due to an overactive thyroid as a result of a goiter. He had been treated with thyroxine 50 µg daily. He recently reported to his physician with complaints of chronic fatigue, weakness, diminished energy, weight gain, and headaches. His serum TSH measured 1.4 mIU/mL (Normal 0.5 – 4.5). A decision was made to continue his current dose of thyroid hormone replacement.
An MRI of the brain was performed to evaluate for the possibility of stroke accounting for his symptoms. The scan demonstrated a 2.5 cm pituitary tumor. Investigations confirmed that he has panhypopituitarism. His TSH was normal. His free T4 and free T3 levels are both extremely low. His thyroid hormone dose has now been increased and he is scheduled for surgery to remove his pituitary tumor.
This patient illustrates one of the often not recognized caveats of panhypopituitarism. Pituitary hormones, like TSH, can be “normal“ but the respective target gland hormones, T4 and T3, can be low or low normal. There are a number of explanations for these observations. Understanding them is key to providing the right dose of thyroid hormone medication for affected patients.
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