Evaluation of thyroid function during growth hormone therapy.
Decrease in the blood levels of PBI, in the thyroidal uptake of iodine, and diminished effect of TRH on TSH release have been reported to occur during growth hormone administration. We assessed thyroid function indices in two groups of growth hormone deficient children before and during long-term HGH therapy. Eight patients were given TSH prior and at 2, 4, and 6 mo of growth hormone treatment. In four other children, the disposal rates of simultaneously administered I125-T4 and I131-T3 were measured before and at 2 and 6 mo after initiation of HGH replacement. Blood levels of TSH, T3, T4, TBG capacity, and the T3 resin uptake were obtained at the time of each study. Growth hormone therapy did not affect the blood levels of T4, T3, TSH, TBG capacity, the T3 resin uptake, the thyroidal response to exogenous TSH, nor the disposal rates of thyroid hormones.