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. 1. Ayodele O, et al. ASBMR 2020, 11−15 Sep 2020.