PTH and hypoparathyroidism: However, in this study, 1-h PTH with a threshold of 10.42pg/ml was better than decline in PTH, with a sensitivity and specificity of 83.4% and 100%.27 It may be that the decline is not better than absolute values because hypocalcaemia may have causes other than hypoparathyroidism and this can in turn affect PTH decline.