Hypothyroidism is diagnosed by serum concentration of TSH above normal (>4.5 mU/L) and that of FT4 below (primary hypothyroidism), although tertiary and secondary hypothyroidism may occur when deficits are at hypothalamic or pituitary levels and both serum TSH and TH concentrations are low (78, 79). The gene discussed is TH; the disease is hypothyroidism.