Pseudo-Central Hypothyroidism

Shehzad Basaria, MD, Kristina Altman, MD, Milena Braga-Basaria, MD

Disclosures

South Med J. 2003;96(2) 

In This Article

Case Report

A 49-year-old woman was referred to the endocrine clinic for evaluation of central hypothyroidism. A month earlier, during a routine appointment with her gynecologist, she had complained of fatigue, lethargy, and weight gain. She reported occasional palpitations. Hypothyroidism was suspected, and thyroid function tests were performed. The tests revealed a thyrotropin level of 0.6 µIU/ml (normal, 0.5-4.5 µIU/ml) and a free T4 value of 0.3 ng/dl (normal, 0.7-1.6 ng/dl). The results were consistent with central hypothyroidism. The patient denied any history of head trauma, surgery, or radiotherapy. There were no symptoms of adrenal insufficiency, and her menstrual cycles were regular. The patient had a 3-year history of depression, for which she was taking fluoxetine. A week before the patient's clinic visit, during a telephone conversation with the patient's gynecologist, it was decided to check her T3 levels (considering her symptoms of occasional palpitations) before obtaining imaging studies. Free T3 level was elevated at 519 pg/dl (normal, 230-420 pg/dl). Isolated T3 toxicosis due to Graves' disease, toxic adenoma, or toxic multinodular goiter was suspected. During evaluation in the endocrine clinic, a review of the patient's medications revealed that she had been taking liothyronine sodium (cytomel), 12.5 µg bid for the previous 7 months as prescribed by her psychiatrist to augment the antidepressant effect of fluoxetine. An examination revealed that the patient had tachycardia (102 beats/min) but did not have proptosis, lid retraction, lid lag, or tremors. The thyroid gland was normal in size and without any palpable nodules, tenderness, or bruit. The patient's reflexes were hyperactive. The patient was told to stop taking T3, and her psychiatrist was informed regarding her symptoms and serum T3 levels.

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