Among patients with both POD1 PTH levels ≥ 20 pg/ml and 6 a.m. POD1 calcium levels ≥ 2.0 mmol/l, 3 (1.0%) went on to develop symptomatic hypocalcaemia, of whom one (0.3%) was treated with intravenous calcium. Here, PTH is linked to Hypocalcemia.