Supplemental Material for: The transient pubertal free thyroxine dip should not be misinterpreted as central hypothyroidism: a case series

Due to the interindividual variation in timing of pubertal onset, this transient fT4 dip occurs at different ages and becomes less apparentwithin an age-specific reference interval (RI).This may result in fT4 concentrations temporarily falling below the lower limit of the RI when age-specific instead of Tanner stage-specific RIs are used.

As thyroid stimulating hormone (TSH) levels usually remain within the age-specific RI, the resulting biochemical profile resembles central hypothyroidism and frequently triggers extensive, butoften unnecessary diagnostic work-ups. </p><p dir="ltr">Case Presentation: We present twocases of asymptomatic adolescents withlow fT4 concentrations in combination witha normal TSH, in whom central hypothyroidism was initially suspected but subsequently excluded.