Thyroid outcome during long-term gonadotropin-releasing hormone agonist treatments for idiopathic precocious puberty.

Purpose: To examine the effects of long-term gonadotropin-releasing hormone agonist (GnRHa) administration on thyroid function in children affected by central precocious puberty (CPP).

Methods: We retrospectively evaluated circulating thyroid hormones in 73 GnRHa-treated girls who were diagnosed with idiopathic CPP. Monthly depot injections (.1 mg/body kg) of leuprorelin acetate (LA) and of triptorelin (TR) were continuously administered for 40.4 +/- .7 months to 34 and 39 CPP patients, respectively. Serum levels of thyrotropin (TSH), free triiodothyronine (FT3), free thyroxine (FT4), and thyroid antibodies were determined at baseline and after 6, 12, 18, 24, 30, 36, and 40 months of GnRHa administration.

Results: While there was no difference in FT4 release (p > .05), FT3 levels significantly declined during both LA and TR treatments from untreated baseline (p < .05). Opposite to circulating FT4 and FT3 values (p > .05), FT3/FT4 ratio was significantly different among LA and TR groups (p < .05). Both GnRHa treatments did not affect TSH secretion (p > .05); however, LA induced lower TSH values than TR (p < .05).

Conclusions: There is no evidence of thyroid dysfunction during both GnRHa treatments, though changes in TSH, FT3, and FT3/FT4 ratios were noted. Finally, monitoring of thyroid activity during GnRHa administration is not required.