Background: Primary hyperparathyroidism (PHPT) is a common endocrine condition, commonly seen with increasing age. In vast majority, it is diagnosed incidentally and causes no particular symptoms. Symptoms are usually related to acute hypercalcaemia or the complications of chronically elevated serum calcium level. Vitamin D deficiency is common among general population and in patients with PHPT. Studies in secondary hyperparathyroidism (SHPT) have shown that parathyroid hormone (PTH) response is affected by age, with those over 80 showing greater rise in PTH levels. We wanted to see if age has a similar impact on PTH response to vitamin D in those with PHPT.

Objectives: To evaluate the impact of age on PTH response to vitamin D insufficiency in those with PHPT.

Methods: Patients with primary hyperparathyroidism (PHPT), attending general endocrine clinic of a district general hospital, were divided into two groups based on age; less than 70 (n=73) and 70 and above (n=61).Each group was subdivided into vitamin D insufficient (VDI) and vitamin D sufficient (VDS) subgroups. We compared calcium and parathyroid hormone levels and forearm BMD (presented as T score) in VDI and VDS subgroups in the two age groups, at the time of diagnosis. Data were analyzed using unpaired t-test and presented as mean ± SEM, using Graphpad Prism 9.0.1.

Results: There was significant difference in Vitamin D levels in VDI and VDS subgroups, in both age groups (<70; mean vitamin D 27.98 vs. 68.44, p<0.0001; ≥70; mean vitamin D 34.44 vs. 75.74, p<0.0001). The two groups were significantly different in terms of age (mean age 58 vs. 76, p<0.0001). Although there was no difference in calcium and forearm BMD in VDI and VDS, in both age groups, those under 70 showed a greater PTH response to vitamin D insufficiency (mean PTH 19.29 vs. 12.91 respectively, p<0.001).

Conclusion: While in SHPT, those with increasing age show greater rise in PTH levels, our data show that in PHPT, younger patients show a greater PTH rise in response to vitamin D insufficiency. Further work is needed to elucidate the underlying mechanisms.

References: [1]Wyskida et al., Parathyroid hormone response to different vitamin D levels in population-based old and very-old Polish cohorts, Experimental Gerontology, Volume 127, 2019, 110735, ISSN 0531-5565, https://doi.org/10.1016/j.exger.2019.110735.

[2]Malik M Z, Latiwesh O B, Nouh F, et al. (August 15, 2020) Response of Parathyroid Hormone to Vitamin D Deficiency in Otherwise Healthy Individuals. Cureus 12(8): e9764. doi:10.7759/cureus.9764

Disclosure of Interests: None declared.