Abstract

Background: Past sun exposure and vitamin D3 supplementation have been associated with a reduced risk of multiple sclerosis (MS). There are no previous longitudinal studies of vitamin D in MS. Objectives: To compare regulation of vitamin D and calcium homeostasis between MS patients and healthy controls. To study correlation of parameters of vitamin D metabolism with MS activity.

Methods: We measured 25-hydroxyvitamin D, intact PTH, calcium, phosphate, magnesium, chloride, alkaline phosphatase, albumin and TSH in serum every three months and at the time of relapses during one year in 23 MS patients and in 23 healthy controls. MRI BOD and T2 activity was assessed every 6 months.

Results: Vitamin D deficiency [S-25(OH)D ≤ 37 nmol/L] was common affecting half of the patients and controls at some time of the year. Seasonal variation of 25(OH)D was similar in the patients and in the controls, but the 25(OH)D serum levels were lower and the iPTH serum levels were higher during MS relapses than in remission. All 21 relapses during the study occurred at serum iPTH > 20 ng/L (2.2 pmol/L), whereas 38% of patients in remission had iPTH ≤ 20 ng/L. MS patients had a relative hypocalcaemia and a blunted PTH response in the winter. There was no correlation between serum 25(OH)D and MRI parameters.

Conclusions: The endocrine circuitry regulating serum calcium may be altered in MS. There is an inverse relationship between serum vitamin D level and MS clinical activity. The role of vitamin D in MS must be explored further.