Adult-onset idiopathic isolated central hypothyroidism: a case report and literature review.

Central hypothyroidism is commonly associated with impaired secretion of other anterior pituitary hormones, while isolated impairment of TRH-TSH-thyroid hormone axis was mostly identified in children and is a result of genetic mutations including TSH beta subunit gene or less commonly TRH receptor gene mutations. There are also a few reports of adult-onset isolated central hypothyroidism due to pituitary adenoma or empty sella. Here we present a case of adult-onset idiopathic isolated central hypothyroidism with no apparent morphological changes of the pituitary. A 52-year-old female patient was referred to our endocrinology clinic for suspicion of central hypothyroidism in December 2007. She had been taking thyroid hormone supplementation for the past four years. She was not sure if the pill contained only T4 or a combination of T3 and T4. In April 2007, she started to notice hair loss, fatigue, and weight gain while she was still on the thyroid hormone supplementation. At that time, TSH was at 1.59 mcU/ml (normal range reference values not available for that lab), free T4 was at 0.6 ng/dl (normal range: 0.8--1.8) and total T3 was at 89 ng/dl (normal range: 60--181). Her other medical problems included orthostatic hypotension and depression for which she took midodrine and trazodone. She was not sure whether any of her family members had thyroid disorders. On physical exam, there was no remarkable finding. Repeated blood test showed free T4 of 1.3 ng/dl (normal range: 0.8--2.7 ng/dl), free T3 of 2.3 pg/ml (normal range: 2.4--4.2 pg/dl) and TSH of 0.02 mcU/ml (normal range: 0.39--4.60 mcU/ml). The concentrations of other pituitary hormones/markers were all within normal ranges. MRI (magnetic resonance imaging) showed a normal pituitary. She started to take levothyroxine 100 mcg daily and her symptoms improved. She developed no other pituitary hormone deficits in the ensuing six years. s t s