Although a number of patients with
generalized resistance to thyroid hormone have been treated with
bromocriptine (Brc), only one previously reported patient with nontumoral TSH-mediated
hyperthyroidism, presumably due to pituitary resistance to
thyroid hormone (PRTH), has been successfully treated with
bromocriptine (Brc). In addition, several studies suggested that the T3 analog
3,5,3'-triiodothyroacetic acid (
Triac) may control
hyperthyroidism in patients with PRTH. In the current study a patient with PRTH diagnosed at age 15 yr underwent separate therapeutic trials with Brc and
Triac, during which time physical parameters, thyroid function tests, systolic time intervals (
STI), and oxygen consumption (VO2) were measured. On Brc
therapy (12.5 mg/day), heart rate decreased (108 to 72/min), TSH decreased (5.7 to 1.2 mU/L), T3 decreased (9.9 to 1.7 nmol/L), free T4 decreased (205 to 21 pmol/L),
STI lengthened (left ventricular ejection time, 0.389 to 0.405 s), and VO2 did not change (164 to 162 mL/min). We found no significant clinical improvement with a maximal dose of
Triac (2.1 mg/day), only minimal reduction in
goiter size; mild decreases in T3 (9.9 to 6.7 nmol/L), free T4 (205 to 113 pmol/L), and TSH (5.7 to 5.4 mU/L); no change in
STI (left ventricular ejection time, 0.389 to 0.401 sec); and an increase in O2 consumption (VO2, 164 to 209 mL/min). Thus, the results favor Brc as effective
therapy for this patient with PRTH.