Endocrine Abstracts

Background: Chronic hypoparathyroidism is a relatively rare disease associated with various complications. The analysis of large databases of patients with chronic hypoparathyroidism is a necessary tool to enhance quality of medical care, as well as to determine the therapeutic approaches and prognostic markers of the disease.

Aims: To describe complications associated with chronic hypoparathyroidism and determine predictors of their development according to the Russian Registry.

Materials and Methods: The cross-sectional, observational, continuous study based on the Russian Registry of patients with hypoparathyroidism was carried out including 708 patients from 64 regions of the Russia. ROC-analysis was used to find cut-off points of predictors positively associated with complications.

Results: Nephrolithiasis was confirmed in 34.6%, nephrocalcinosis - in 11.7% of cases, 24.9% of patients met the criteria of CKD 3a-5 stages (glomerular filtration rate (GFR)-EPI less than 60 ml/min/1.73 m²). The predictors of renal complication were non-target 24 h urinary calcium level (P=0.033, U-test, Benjamini-Hochberg correction P ₀=0.004) and upper-reference range serum calcium level (P<0.001, U-test, P ₀=0.05). Patients with preserved renal function took significantly lower doses of alfacalcidol - 1.00 µg/day [0.75; 2.00] vs 1.50 µg/day [1.00; 2.00] compared with patients with an GFR less than 60 ml/min/1.73 m² (P=0.033, U-test, P ₀=0.025). Differences in doses of calcium carbonate weren’t obtained (P=0.270, U-test). ROC-analysis revealed cut-off points of serum calcium level associated with the risk of GFR less than 60 ml/min/1.73 m²: 1.97 for albumin-adjusted (AUC=0.651), 2.12 for total (AUC=0.610) and 1.08 for ionized (AUC=0.637) calcium levels. The cut-off point for the decreasing GFR was duration of hypoparathyroidism–14.5 years, with a 3.58-fold increased risk. Also the excess of 24 h urinary calcium level more than 4.02 mmol/day was associated with an increased risk of structural disorders in the kidneys (AUC=0.594). The cataract was confirmed in 47% patients, 82% of them had postsurgical hypoparathyroidism. The longer duration (10.5 years [6.0; 17.0] vs 6 [4.0; 9.0]) of hypoparathyroidism was associated with more frequent cataract (P<0.001, U-test, P ₀=0.004) and this does not depend on medicaments and their doses. ROC-analysis showed cut-off points of serum ionized calcium level of 1.03 mmol/l, if it is not reached, the risk of developing cataracts increases (AUC=0.652). The cut-off point for the development of cataracts was duration of hypoparathyroidism–10.5 years, with a 4.39-fold increased risk.

Conclusions: Hypoparathyroidism is associated with higher risks of renal stone formation, decreased GFR, cataract - especially in patients with longer duration of disease. The non-target serum calcium level was associated with renal and ophthalmological complications.