The natural history of the hyperthyrotropinemia of children born prematurely

Objective: Non-autoimmune hyperthyrotropinemia has been previously reported among children born prematurely. The aim of this study was to follow up their thyroid function, volume, and structure and to investigate the relationship with growth, IGF-I, lipid profile, and insulin sensitivity. Methods: Seventy-two children born prematurely (33.2 +/- 2.2 weeks), 26 appropriate (AGA) and 46 small for gestational age (SGA), were evaluated at the age of 7.6 +/- 2.3 yr (time 1) and at the age of 11.4 +/- 2.3 yr (time 2). We also measured TSH, free T-3 (fT(3)), free T-4 (fT(4)), thyroperoxidase antibodies (TPO-Ab), thyroglobulin antibodies (TG-Ab), thyroid ultrasound, auxological parameters, lipid profile, glucose, and insulin level. Results: In the AGA group TSH was similar in both times (2.7 +/- 1.0 vs 3.0 +/- 0.9 mU/l) and above the upper normal limit in 4 (15.4%) subjects at time 1 and in 6 (23.7%) subjects at time 2 (ns). In the SGA group, TSH was similar in both times (2.8 +/- 1.2 vs 2.5 +/- 1.0 mU/l) and above the upper normal limit in 11(23.9%) subjects at time 1 and 5 (10.8%) subjects at time 2 (ns). fT(4) and fT(3) were always normal and TPO- and TG-Ab absent. Thyroid volume increased progressively, but significantly only in the AGA group (p=0.0005). The thyroid structure was always normal and there was no influence on the growth and the biochemical profile. Conclusions: Some ex-premature babies show a mild and variable thyroid dysfunction, which does not seem to evolve toward an overt thyroid dysfunction.