A new meta-analysis is out that says vitamin D supplementation is an okay measure to take in primary hyperparathyroidism.
Primary hyperparathyroidism (PHPT) is a condition where the parathyroid glands develop an adenoma, which is a non-cancerous tumor. This adenoma causes your parathyroid to produce too much parathyroid hormone, which can lead to a condition where you have too much calcium in your blood (hypercalcemia) and can compromise your bone health and cause osteoporosis.
Since vitamin D can increase your ability to absorb calcium in the gut, doctors are usually cautious to prescribe or recommend vitamin D, worried that it might tip your calcium balance a little too high.
But are these concerns unfounded? Last July, I reported on an observational study that looked at 28 patients with mild PHPT who supplemented with vitamin D. They found no increase in calcium levels in the patients and decrease in parathyroid levels, suggesting that vitamin D is not only safe, but maybe necessary.
Recently, a meta-analysis was published in Clinical Endocrinology that looked at 10 studies similar to the one in July. The strength in performing a meta-analysis is that we can pool more patients together and feel more confident in its results compared to a small study.
The researchers gathered the 10 studies after searching the Medline, Embase and Cochrane databases. All of the studies were observational since there are no randomized controlled trials examining the issue. However, the observational studies did look at patients who were supplementing with vitamin D.
In total, these studies involved 340 mild PHPT patients that supplemented with vitamin D. The duration of the supplementation/observation period in the studies ranged from 1.25 months to 12 months.
What did the researchers find? Were these PHPT patients at risk of high serum calcium? Here were the findings:
- Mean serum vitamin D levels increased by 22.1 ng/ml. Eight of 10 studies brought vitamin D levels above 30 ng/ml.
- There was no change in serum calcium levels, the major concern in PHPT (-.08, 95%: -0.2, +0.03, P = 0.2)
- 227 patients took vitamin D for more than 6 months. When the researchers looked at incidence of hypercalcemia (high calcium) in these patients, only 5 patients developed high serum calcium. Therefore, the incidence of hypercalcemia was 2.2% with vitamin D supplementation in PHPT subjects.
- There was a significant reduction in PTH levels by 3.5 pmol/L (-5.8, -1.2, P = 0.003).
The researchers concluded,
“Vitamin D replacement in mild PHPT with coexistent vitamin D deficiency reduces parathyroid levels significantly without exhibiting hypercalcemia or hypercalciuria. There is certainly a need for a large RCT with vitamin D replacement in asymptomatic PHPT with coexistent vitamin D deficiency with long term follow up to address the many questions which remain unanswered.”
The authors further pointed out that researchers in the past often cautioned against taking vitamin D in PHPT, however this is based on expert opinion and is not evidence-based, as shown in this meta-analysis. It appears at least in mild PHPT, vitamin D supplementation is safe over 97% of the time.
Also keep in mind that these 10 studies looked at mild PHPT, so we still need more research in moderate and severe cases. And, we could use randomized controlled trials for mild, moderate and severe cases.
Shah VN et al. Effect of 25 (OH) D replacements in patients with primary hyperparathyroidism (PHPT) and coexistent vitamin D deficiency on serum 25(OH) D, calcium and PTH levels: A meta-analysis and review of literature. Clin Endocrinol, 2014.