SAN DIEGO – The prevalence of unsuspected primary hyperparathyroidism among patients diagnosed with fibromyalgia was 11% in a small exploratory study, Dr. Michael Tsoukas reported at the annual meeting of the American College of Rheumatology.
That’s roughly 100-fold greater than the prevalence of primary hyperparathyroidism in the general population, noted Dr. Tsoukas of McGill University, Montreal.
The classic symptoms of primary hyperparathyroidism include musculoskeletal pain, fatigue, mood disorders, and sleep disturbances, a clinical picture closely mimicking that of fibromyalgia, he observed.
Dr. Tsoukas presented a retrospective study of a convenience sample of 38 consecutive patients with a primary diagnosis of fibromyalgia attending a multidisciplinary tertiary care pain center where physicians obtained routine blood tests. Four of the 38, or 11%, met criteria for the biochemical diagnosis of hyperthyroidism. Two had what’s known as normohormonal hyperparathyroidism, marked by a serum ionized calcium elevated above 1.32 mmol/L or 5.3 mg/dL, with inappropriately high parathyroid hormone levels. The other two had a parathyroid hormone level in excess of 9.3 pmol/L or 93 pg/mL, with inappropriately nonsuppressed calcium.
This was a pilot study. Four cases of unsuspected hyperparathyroidism hardly make for a definitive study. But this was the first study to look at hyperparathyroidism in fibromyalgia patients, and given how common fibromyalgia is and the difficulties and frustrations often encountered in its treatment, these intriguing preliminary findings warrant large, prospective, multicenter studies to further clarify the relationship between these two disorders with closely similar symptoms, Dr. Tsoukas concluded.
He reported having no financial conflicts of interest in this unfunded study.