Konishi A, Ida S, Shoji Y, et al. - Provided that abnormalities in the hypothalamic‐pituitary‐thyroid (HPT) axis have been implicated in Prader‐Willi syndrome (PWS), however, insufficient evidence is currently available on age‐dependent alterations in the HPT axis, researchers examined age‐dependent variations in PWS children's thyroid hormone levels. Free T4 (FT4), free T3 (FT3) and thyroid‐stimulating hormone (TSH) concentrations were contrasted retrospectively between genetically confirmed PWS children (N = 43, median age: 11.2 months) and controls (N = 85, median age: 14.5 months) matched for age, gender, body weight‐SD score (SDS), height‐SDS, body mass index‐SDS and serum albumin level, a marker of the nutritional status. Infants with PWS had lower levels of FT4, but FT3 levels were normal, implying that routine levothyroxine replacement therapy might not be appropriate.