Central hypothyroidism improves with age in very young children with Prader-Willi syndrome.

ABSTRACT

OBJECTIVE: Abnormalities in the hypothalamic-pituitary-thyroid (HPT) axis have been implicated in Prader-Willi syndrome (PWS); however, limited information is currently available on age-dependent alterations in the HPT axis. We herein investigated age-dependent differences in thyroid hormone levels in PWS children. DESIGN/PATIENTS/MEASUREMENTS Free T4 (FT4), free T3 (FT3) and thyroid-stimulating hormone (TSH) concentrations were retrospectively compared between genetically confirmed PWS children (N = 43, median age 11.2 months) and controls (N = 85, median age 14.5 months) matched for age, sex, body weight-SD score (SDS), height-SDS, body mass index-SDS and serum albumin level, a marker of the nutritional status. Subjects were subdivided into two groups based on their age an infant group aged between 1 and 11 months (PWS N = 22, controls N = 30) and a toddler group aged between 12 and 47 months (PWS N = 21, controls N = 55). None of the subjects had ever been treated with growth hormone or levothyroxine. RESULTS: After adjustments for confounding variables, in the infant group, FT4 levels (pmol/L) were significantly lower in PWS (11.24 in PWS vs 14.32 in controls, P = .0002), whereas no significant differences were observed in FT3 or TSH levels. In the toddler group, no significant differences were noted in FT4 (12.23 in PWS vs 15.31 in controls, P = .10), FT3 or TSH levels. The FT3/FT4 ratio was significantly increased in PWS in both groups. FT4 levels were positively correlated with age in PWS. CONCLUSIONS: Infants with PWS had lower FT4 levels, but FT3 levels were normal, indicating that the levothyroxine replacement therapy may not need to be routinely performed.