Long-term follow-up of patients with hypoparathyroidism

Abstract

Context: Despite tremendous interest in hypoparathyroidism, large cohort studies describing typical treatment patterns, laboratory parameters, and rates of complications are lacking.

Objective: Our objective was to characterize the course of disease in a large cohort of hypoparathyroid patients.

Design and setting: We conducted a chart review of patients with permanent hypoparathyroidism identified via a clinical patient data registry. Patients were seen at a Boston tertiary-care hospital system between 1988 and 2009.

Patients: We identified 120 patients. Diagnosis was confirmed by documented hypocalcemia with a simultaneous low or inappropriately normal PTH level for at least 1 yr. Mean age at the end of the observation period was 52 ± 19 (range 2-87) yr, and the cohort was 73% female.

Main outcome measure: We evaluated serum and urine laboratory results and renal and brain imaging.

Results: We calculated time-weighted average serum calcium measurements for all patients. The time-weighted average for calcium was between 7.5 and 9.5 mg/dl for the majority (88%) of patients. Using linear interpolation, we estimated the proportion of time within the target calcium range for each patient with a median of 86% (interquartile range 67-98%). Of those with a 24-h urine collection for calcium (n = 53), 38% had at least one measurement over 300 mg/d. Of those with renal imaging (n = 54), 31% had renal calcifications, and 52% of those with head imaging (n = 31) had basal ganglia calcifications. Rates of chronic kidney disease stage 3 or higher were 2- to 17-fold greater than age-appropriate norms.

Conclusions: Hypoparathyroidism and its treatment carry a large burden of disease. Renal abnormalities are particularly common.

Fig. 1.

Distribution plot of the most recently recorded serum calcium (A), serum phosphorus (B), and serum calcium-phosphate product (C) for each patient in the cohort. Unshaded areas represent target ranges for each measurement.

Fig. 2.

Plot of proportion of observed time with serum calcium between 7.5 and 9.5 mg/dl (green), <7.5 mg/dl (yellow), or >9.5 mg/dl (orange). Each column represents one patient in the cohort.

Fig. 3.

Urine calcium parameters. A, Distribution plot of the most recently recorded 24-h urine calcium value (n = 53); ▵, patients prescribed a thiazide medication. B, Scatterplot of all 24-h urine calcium levels with serum calcium levels recorded the same day (n = 44, representing 22 patients). Unshaded areas represent target range (<300 mg).

Fig. 4.

Flowchart representing number of patients with renal and head imaging and the number with renal and basal ganglia calcifications.

Fig. 5.

Proportion of patients with eGFR below 60 ml/min · 1.73 m² by age group. Gray columns, hypoparathyroid cohort; black columns, population norms. *, P < 0.001 for comparison by one-sample t test.