FHH is a highly penetrant autosomal dominant condition characterised by lifelong non-progressive mild-to-moderate hypercalcaemia, normal (in ~80% of patients) or mildly raised serum PTH levels (in ~20% of patients) (Firek et al. 1991), and low urinary calcium excretion (in ~95% of patients) (Marx 2015). The gene discussed is PTH; the disease is Hypercalcemia.