Endocrine Abstracts

Introduction: In chronic hypoparathyroidism (cHP), hypercalciuria is frequent, the mechanism of which remains unclear. The repetition of episodes of urinary tract obstruction by lithiasis can play a key role in the progressive deterioration of renal function. Taking advantage of the prospective cohort Epi-Hypo, we examined the relationship between nephrolithiasis and hypercalciuria.

Methods: The Epi-Hypo cohort started in 2016 in France and is still actively recruiting. Inclusion criteria include i) chronic (i.e. ≥6 months) cHP, ii) patient followed in France, and iii) patient agreement to participate. Exclusion criteria include i) transient cHP and ii) pseudo-hypoparathyroidism. Both pediatric and adult participants are recruited by physicians. Data are collected online through a secure digital platform for: demographics, circumstances of diagnosis, and follow-up (clinical events such as nephrolithiasis, as well as biology including calciuria) and entered in the database by physicians.

Results: The database was frozen on March 1st, 2023. At that time, urinary excretion of calcium was available for 776 patients; 74% were female and the median [IQR] age at diagnosis was 43 [31;56] years. Neck surgery accounted for 73% of cases. Hypercalciuria (defined as urinary calcium excretion >7.5 mmol/d in men and >6.25 mmol/d in women) was present in 258 (33%) of study patients. The proportion of patients with nephrolithiasis was significantly higher in patients with than in patients without hypercalciuria (26 vs 17%, P=0.023). Age, gender, or cause of hypoparathyroidism did not differ between patients with or without nephrolithiasis. The percentage of patients with hypercalciuria treated by oral calcium or active vitamin D was significantly higher than that of patients without hypercalciuria (72% vs 52%; 78% vs 65%, respectively; P<0.05 for both). Alternatively, hypercalciuric patients received significantly less often 25(OH)vitamin D (28% vs 35%; P=0.024).

Discussion/Conclusion: These data indicate that nephrolithiasis is more prevalent in cHP patients with hypercalciuria. The follow-up of this population may allow to assess a causal relationship between hypercalciuria and nephrolithiasis. It further suggests that normalization of urinary calcium excretion is a key therapeutic objective in patients with cHP hypoparathyroidism. Its impact on renal function remains to be investigated.