Endocrine Abstracts

Introduction

A high calcium-phosphate product is thought to increase the risk of soft tissue calcification in hypoparathyroidism, including cataracts. Based on small case series, cataracts in hypoparathyroidism typically develop in the posterior subcapsular region of the lens. However, the mechanism of cataract formation is still not well understood.

Materials and methods

In a large cohort of 1014 patients with biochemically confirmed hypoparathyroidism diagnosed between 2000 and 2020, we identified those with incident non-traumatic cataracts. Etiology and date of diagnosis of hypoparathyroidism were determined by medical records review. Information on type of cataract, date of surgery and complications after surgery was also collected. Three age- and sex- matched controls with cataracts without hypoparathyroidism were selected for each case.

Results

A total of 96 patients received a new diagnosis of cataracts over this 20-year interval. Of these, 81 had postsurgical and 15 nonsurgical hypoparathyroidism. Median age at hypoparathyroidism diagnosis was 50.0 ± 19.2 years (range, 0–80), and duration of hypoparathyroidism was 17.1 ± 15.0 (0.6–56) years, with no significant differences between postsurgical and nonsurgical groups. Median age at diagnosis of cataracts was 70.4 ± 13.8 (range, 17–88), with older age in the postsurgical group (71.0 ± 10.2 vs. 58.2 ± 22.7, P = 0.028). We identified four categories of cataracts (nuclear sclerosis or age-related, cortical, posterior subcapsular and combined forms)in 57 patients with hypoparathyroidism and 198 controls. Age-related cataracts were the most frequent form in controls (82.8%), while these were less frequent (59.6%) in patients with hypoparathyroidism. Opacities in the cortical and subcapsular portion of the lens were much more common in hypoparathyroidism (40.4% vs. 17.1%), and combinations of the three types were more common in hypoparathyroidism compared to controls (17.5% vs. 2.5%). The lower tertile of time-weighted average of serum calcium (K = –0.244, P < 0.001, N = 191) and the higher tertile of time-weighted average of serum phosphate (K = 0.183, P = 0.026, N = 148) were associated with greater prevalence of cortical, posterior subcapsular and combined forms of cataracts in the total study population. Posterior subcapsular cataracts alone were equally common in patients and controls (8.8% vs. 10.1%, P = NS). Nonsurgical hypoparathyroidism had the highest prevalence of non-age- related cataracts (8/15, 57%). Hypoparathyroidism did not affect age of diagnosis, type, or complications of cataract surgery, including posterior capsule opacification after surgery.

Discussion

Peripheral damage to the lens is characteristic of hypoparathyroidism and may be correlated with hypocalcemia and hyperphosphatemia. Control of these biochemical abnormalities may reduce the risk of this complication.