Unfortunately, her father declined genetic or biochemical evaluation, and thus we cannot exclude maternal isodisomy or a paternal deletion involving TRHR. Biochemical and radiological features in our patient (T4 levels 74% of the lower limit of normal, detectable TSH, normal basal prolactin, and normal pituitary magnetic resonance imaging) are concordant with previous cases and contrast with the profound hypothyroidism typically seen in children with TSHB mutations. The gene discussed is TSHB; the disease is hypothyroidism.