Prevalence of primary hyperparathyroidism in a referred sample of fibromyalgia patients.

The objective of this study is to determine the prevalence of primary hyperparathyroidism in a referred sample of fibromyalgia patients. Consecutively, referred patients with confirmed fibromyalgia (FM group) had measurements of serum levels of vitamin D, alkaline phosphatase, total calcium, magnesium, phosphate, creatinine, total protein, albumin, and parathyroid hormone. The same measurements were also conducted in a group of patients with widespread pain (WP group) who did not meet the 2010 Modified ACR criteria for fibromyalgia and a group with localized musculoskeletal pain (MSK group). A case of primary hyperparathyroidism was defined as a subject whose results showed any of the following: (1) parathyroid hormone levels above 6.8 pmol/L; (2) an ionized calcium above 1.25 mmol/L; or (3) both elevated, in the presence of normal range creatinine, alkaline phosphatase, vitamin D, phosphate, and magnesium. The mean age and the proportion of subjects who met the case definition of primary hyperparathyroidism were calculated for all groups. There were 125 subjects in the FM group, 127 in the WP group, and 138 in the MSK group. The prevalence rates of primary hyperparathyroidism were 6.4, 5.5, and 6.1%, respectively, for these groups. Comparison of these prevalence rates to published figures for general clinical and non-clinical populations reveals no differences. The prevalence of primary hyperparathyroidism in fibromyalgia patients is not different than that in other patients with WP or those with localized pain, nor is it likely different than that seen in the general population.