1 From the Departments of Pediatrics and Internal Medicine, Divisions of Pediatric Endocrinology and Nuclear Medicine, the University of Michigan Medical Center, Ann Arbor
The diagnosis of partial peripheral and pituitary resistance to thyroid hormone was ultimately made in two boys, 7 and 9 years of age, and a 10-year-old girl who had goiters and hyperthyroxinemia. The boys were treated with propythiouracil and/or thyroidectomy or iodine 131 for suspected thyrotoxicosis but had poorly suppressible serum thyroid-stimulating hormone (TSH) post treatment in spite of the usual L-thyroxine replacement. The girl had increasing goiter size while receiving propylthiouracil, 100 mg every eight hours. These findings led to reevaluation of thyroid hormone dynamics in these children and their families. Twelve additional family members, 3 to 38 years of age, compatible with an autosomal dominant inheritance, were also found to have peripheral and pituitary resistance to thyroid hormone. All affected individuals had elevated serum thyroxine and triiodothyronine levels, normal to slightly elevated triiodothyronine resin uptakes, and a nonsuppressed serum TSH. The five individuals who were given thyrotropin-releasing hormone showed exaggerated TSH responses, which normalized on L-thyroxine therapy. Misdiagnosis in six of 15 family members led to significant morbidity (hypothyroidism, delayed growth, and therapy risk). A nonsuppressed serum TSH in a patient with suspected thyrotoxicosis should lead to suspicion of this disorder. Appropriate management for this condition includes L-thyroxine therapy to decrease goiter size and normalize TSH responses to thyrotropin-releasing hormone.
Key Words: thyroid hormone resistance thyrotoxicosis
Submitted on November 18, 1985
Accepted on March 27, 1986