To what degree does a Vitamin D course mitigate the effects of Primary Hyperparathyroidism?

Question

Primary Hyperparathyroidism, often caused by a parathyroid gland having an adenoma on it, increases the release of the parathyroid hormone (PTH) in the body. This causes the excess release of calcium from bones into the blood, and the weakening of said bones. A low Vitamin D level often accompanies hyperparathyroidism (or perhaps is a result of?) and while most calcium is excreted then through urine, some of it forms into kidney stones.

Recently, some studies show, and consequently some doctors now recommend, a course of vitamin-D to re-absorb the calcium that had been released.

Given a patient with low vitamin D, a calcium level of 2.9 mmol/L and PTH level of 12.9 mg/dl, what would be the expected impact of a course of Vitamin D at 50,000 IU/week ?

Would the effects of hyperparathyroidism be fully mitigated while on the course, or if not, to what degree would they be?

Answer 1

If you see a low vitamin D level in conjunction with a raised PTH level, then I think you need to think secondary hyperparathyroidism (HiPTH). But since vast numbers of most western populations have lowish vitamin D levels seen even in my own clinic [3] where sun shine levels are high then it may be just co-incidental. HiPTH disease should not lower the D3 levels. And in secondary HiPTH disease the calcium and phosphate should be subnormal.

If the person is from the Indian subcontinent, then the matter changes somewhat. These people often have defective vitamin D handling so that they develop autonomous hyperparathyroidism if not actually tertiary hyperparathyroidism. Calcium is then high. [1]

As for the actual question of vitamin D supplementation in the case of primary hyperparathyroidism (PHPT), then there's good reason to make sure the person is at least replete with vitamin D so that you don't get secondary HPTH disease in addition to the primary HPTH disease. This is likely the scenario you have posted. As for treating vitamin D deficiency to reach supranormal levels in the presence of primary HPTH disease, I don't believe that there is role for that as found in the following study which looked at Vitamin D in PHPT disease

In summary, our findings demonstrate that low vitamin D, using a threshold of <20 but not <30 ng/mL, is associated with more biochemically severe PHPT, as manifested by higher PTH levels. Although vitamin D insufficiency was associated with modest cortical effects upon the skeleton, low vitamin D levels using the current thresholds were not associated with evidence of more severe disease as reflected by symptoms or meeting criteria for parathyroidectomy. As secular trends in vitamin D supplementation extend into PHPT populations, cohorts such as this one, with less vitamin D deficiency, are likely to become more common. We conclude that in this PHPT cohort with few profoundly vitamin D-deficient patients, vitamin D status did not appear to significantly impact clinical presentation or aBMD. [2]

1. Vitamin D metabolism is altered in Asian Indians in the southern United States: a clinical research center study. J Clin Endocrinol Metab. 1998;83(1):169.

2. Vitamin D in Primary Hyperparathyroidism: Effects on Clinical, Biochemical, and Densitometric Presentation 2105 https://academic.oup.com/jcem/article/100/9/3443/2830141

3. Vitamin D deficiency among patients attending a central New Zealand rheumatology outpatient clinic. Chiu, G N Z Med J. 2005 Nov 11;118(1225):U1727.