EFFECTS OF GROWTH HORMONE REPLACEMENT THERAPY ON THYROID FUNCTION TESTS IN GROWTH HORMONE DEFICIENT CHILDREN

There are numerous, often contradictory reports on the effect of growth hormone (GH) therapy on thyroid function. These reports prompted us to evaluate the impact of GH therapy on thyroid function in previously euthyroid children with GH deficiency. Twenty five clinically and biochemically euthyroid children with GH deficiency were studied. A thyroid profile (T4, Free T4, T3 and TSH) was performed at baseline and 3, 6 and 12 months after GH therapy in 21 children with idiopathic growth hormone deficiency (group A) and 4 children with organic GH deficiency (group B). We observed a significant reduction in serum T4 and free T4 concentrations during GH therapy in both groups (P < 0.01). No patient in group A had free T4 levels fell into the hypothyroid range, while in one of four patients in group B, free T4 value fell into the hypothyroid range during GH therapy. In both groups, no significant variation in serum TSH and T3 was recorded at any time. Our data suggest that GH therapy can introduce changes in thyroid function and so confirm the need of a careful monitoring of thyroid function in particular in children with organic GH deficiency during long-term GH therapy.