[Differential diagnosis of hypoparathyroidism and the Ellsworth-Howard's test]

Presence of hypocalcemia along with normo- or hyper-phosphatemia in the absence of decreased renal function strongly suggests hypoparathyroidism. The first step of differential diagnosis is the measurement of serum intact-PTH level. Less than 30 pg/mL of serum intact-PTH means decreased secretion of PTH, most often associated with post-surgical or idiopathic hypoparathyroidism, and hypomagnesemia. Serum intact-PTH values of 30 pg/mL or more suggest psuedohypoparathyroidism (PHP). In the latter case, to confirm decreased PTH responsiveness, Ellsworth-Howard's test or PTH loading test should be performed.