Endocrine Abstracts

Pituitary resistance to thyroid hormone is a very rare cause of hyperthyroidism. It is characterized by normal, or elevated TSH concentration with high concentration of thyroxine and triiodothyronine.

Here, we present a case of a 24-year-old woman who suffered from mild thyrotoxicosis and diffuse goiter for ten years. For several years she was under treatment with methimazole, but without any significant improvement, apart from the enlargement of the thyroid. She had elevated free and total thyroxine and triiodothyronine with slightly elevated TSH concentration. Sonography revealed normoechogenic, slightly enlarged thyroid gland. Pituitary adenoma was excluded as magnetic resonance imaging showed normal pituitary gland, alpha-subunit was within normal range and serum TSH concentration increased after TRH administration. Thus, the diagnosis of the syndrome of pituitary resistance to thyroid hormone was established. She was given bromocriptine at a dose of 10 mg per day. After 12 months of treatment she has no longer signs of thyrotoxicosis, her serum TSH and free thyroxine and triiodothyronie remain within normal range, and thyroid volume significantly diminished. The tolerance of the treatment is good.

In conclusion, we strongly recommend bromocriptine treatment for the pituitary resistance to thyroid hormone syndrome as a safe, well-tolerated and effective treatment.