Background: Several studies have investigated the effects of GH replacement therapy (GHRT) on thyroid function in children with GH deficiency (GHD) leading to contrasting results. Indeed, GHRT has been reported to affect the peripheral metabolism of thyroid hormones, to alter TSH secretion by pituitary and to unmask secondary hypothyroidism.
Objective: To evaluate long-term effects of GHRT on thyroid function in a large cohort of GHD children.
Methods: Sixty-five children (40 M) aged 9.47±3.73 years with isolated GHD were studied before and during the first three years of GHRT. Clinical parameters (height, weight, BMI and growth velocity) and serum TSH, FT4, FT3 and IGF-1 levels were evaluated at baseline, after 6 months of GHRT and then annually.
Results: At study entry, all GHD children were euthyroid and none became hypothyroid during the follow-up. Six months of GHRT were associated with reduction in FT4 levels (P<0.05) and increase in FT3 levels (P<0.05) even though they were still normal associated with no differences in TSH concentrations. No further modifications were observed in the following years of therapy (Table 1).
|Baseline||6 months||1 year||2 years||3 years|
|Growth velocity (SDS)||−2.57±1.45||3.30±2.63a||3.09±3.16||2.65±3.21||1.62±2.81|
|a P < 0.05 vs Baseline|
Conclusion: GH replacement treatment in GHD children was associated with a persistent decrease of FT4 concentrations which however remained within reference ranges. No effects on other markers of thyroid function were detected. Whether these mild changes may have a clinical impact should be further investigated with long-term studies.
18 - 21 May 2019
European Society of Endocrinology