Serum Calcium Levels in Adult Patients With Chronic Hypoparathyroidism Treated With rhPTH(1-84) Compared With a Historical Control Cohort

Adult patients (pts) with chronic hypoparathyroidism (HypoPT) have wide fluctuations in albumin-corrected serum calcium (Ca) measurements.1 This study assessed Ca levels over a 5-yr period in adult pts with chronic HypoPT treated with or without recombinant human parathyroid hormone (1-84), rhPTH(1-84). The rhPTH(1-84)- treated pt cohort was from NCT01297309 (RACE) and NCT01199614 (HEXT) clinical trials. A historical control pt cohort with chronic HypoPT who did not receive rhPTH(1- 84) or rhPTH(1-34) came from the US Explorys electronic medical record database (Jan 2007-Aug 2019); selection criteria were similar to those used for the rhPTH(1-84)- treated cohort. The index date was the day after initiation of treatment for the rhPTH(1-84) cohort and the day after the first calcitriol prescription for the control cohort. Pts were required to have ≥1 pair of serum albumin and Ca values occurring on the same date during the 6 months before index and 5 yrs (±6 months) after index. For pts from RACE, baseline and study visit data after rhPTH(1-84) initiation were collected from the antecedent trials. Specified ranges for albumin-corrected serum Ca values were: <7.5 mg/dL (<1.875 mmol/L); ≥7.5-<8.0 mg/dL (≥1.875-<2.0 mmol/L); ≥8.0-<9.0 mg/dL (≥2.0-<2.25 mmol/L); ≥9.0-<10.2 mg/dL (≥2.25-<2.55 mmol/L); and ≥10.2 mg/dL (≥2.55 mmol/L). Changes in Ca levels were assessed using multivariable regression models. There were 71 pts in the rhPTH(1-84) cohort and 119 pts in the control. Before the index date, rhPTH(1-84)-treated pts, compared with the control, were younger (mean±SD, 47.8±10.8 vs 54.9±15.5 years; P<0.001) and a lower proportion had acute manifestations of HypoPT (22.5% vs 64.7%; P<0.001). Over a 5-yr period, in adjusted analyses rhPTH(1-84)-treated pts, compared with the control, had a similar mean proportion of <7.5 mg/ dL Ca measurements per pt (13.1% vs 13.1%; P=0.41), a higher proportion of ≥7.5-<8.0 mg/dL Ca measurements per pt (18.8% vs 10.6%; P<0.001), a similar proportion of ≥8.0-<9.0 mg/dL Ca measurements per pt (50.7% vs 48.5%; P=0.68), a lower proportion of ≥9.0-<10.2 mg/ dL Ca measurements per pt (15.6% vs 24.1%; P<0.001), and a lower proportion of ≥10.2 mg/dL Ca measurements per pt (1.9% vs 3.7%; P=0.27). The rhPTH(1-84) cohort, compared with the control, had a higher proportion of pts with target range Ca measurements ≥7.5-<9.0 mg/ dL (≥1.875-<2.25 mmol/L) for at least 50% of their values (88.7% vs 62.2%; P<0.001). Data interpretation is limited by the differing pt management (ie, trial protocols for the rhPTH[1-84] cohort and clinical practice for the control cohort). Over a 5-yr period, per pt serum Ca levels fluctuated in pts with chronic HypoPT, but levels were more stable in pts treated with rhPTH(1-84) and a lower proportion had hypercalcemia, compared with controls.