No differences in either bone mineral density or serum 25OHD levels have been found between 205 women with fibromyalgia (both pre- and postmenopausal) and their controls. However, a lack of the expected 25OHD summer rise was observed in patients.
Contradictory data have been published regarding a possible association between fibromyalgia and osteoporosis or hypovitaminosis D. Most studies, however, have been performed in small size samples and have excluded postmenopausal women. We decided to study this association in a larger sample of fibromyalgia patients including both pre- and postmenopausal women.
Two hundred five patients were recruited from a clinic specializing in fibromyalgia and 205 healthy controls were enrolled from the census of a Primary Care Center. Controls were matched with patients by age and the time of the year they were included in the study. Bone mineral density (BMD) was measured by DXA. Serum 25OHD, iPTH, P1NP, and CTX were also determined.
BMD was similar in both groups (lumbar spine, 0.971 ± 0.146 g/cm(2) in patients and 0.970 ± 0.132 g/cm(2) in controls; femoral neck, 0.780 ± 0.122 g/cm(2) and 0.785 ± 0.117 g/cm(2), respectively). 25OHD levels were also similar: 23.0 ± 9.5 ng/ml and 24.1 ± 9.6 ng/ml. However, while controls showed the usual summer rise in 25OHD, fibromyalgia patients did not. PTH did not show seasonal changes, but on average was higher in patients (51 pg/ml vs. 48 pg/ml; p = 0.034). P1NP or CTX were similar in both groups.
No differences in BMD were found between patients and controls. As for 25OHD, a lack of its expected summer rise was observed. It is doubtful whether this has any homeostatic consequence. We consider that the association reported in other studies is merely circumstantial, and not due to the intrinsic characteristics of these disorders.