Muscle Cramps Do Not Improve With Correction of Vitamin D Insufficiency.

BACKGROUND: Minimal treatment options exist for idiopathic muscle cramps. OBJECTIVE: We evaluated whether correction of vitamin D insufficiency relieved muscle cramps in postmenopausal women. METHODS: We conducted a post hoc analysis of a randomized, double-blind, placebo-controlled trial at a single academic medical center in the Midwest to evaluate the benefits of treating vitamin D insufficiency. Two hundred thirty postmenopausal women participated. Eligible women were ≤75 years old, 5 years past menopause or oophorectomy, or ≥60 years if they had previously undergone hysterectomy without oophorectomy. Women had vitamin D insufficiency at baseline (25-hydroxyvitamin D 14-27 ng/mL). We excluded subjects with a glomerular filtration rate <45 mL/minute. INTERVENTIONS FOR CLINICAL TRIALS: Participants completed food diaries, laboratory studies, and functional tests including the Timed Up and Go test, Physical Activity Scale for the Elderly, Health Assessment Questionnaire (a measure of disability), and pain scores. Subjects recorded muscle cramp frequency and severity using a standardized form at 6 visits over 1 year. RESULTS: During the trial, over half of participants (n=121, 53%) reported muscle cramps. Despite unequivocal vitamin D repletion, vitamin D had no effect on muscle cramps. Pain levels, disability, and dietary potassium predicted presence of cramps. Serum albumin and physical activity were inversely associated with, and disability was positively associated with, severity of muscle cramps. CONCLUSIONS: Further studies are needed to evaluate the link between pain, disability, dietary potassium intake, and muscle cramps.

Hypocalciuria as a Predictor of Reduced Intestinal Calcium Absorption.

Impaired intestinal calcium absorption contributes to osteoporosis, but its measurement is limited to research settings. We hypothesized that 24-hour urine calcium (24HUC) values could diagnose low fractional calcium absorption (FCA). We performed a post hoc analysis of clinical trial data to determine whether 24HUC predicted low FCA compared with the gold standard dual calcium isotope method. Two hundred thirty postmenopausal women <75 years old without osteoporosis underwent 445 FCA measurements using calcium isotopes (8 mg of oral 44Ca, 3 mg of intravenous 42Ca) and a 24-hour inpatient urine collection at 0 and 12 months. We determined subjects' total calcium intake via review of food diaries and supplements. Net calcium absorption (NCA) was total calcium intake × FCA. NCA and 24HUC values demonstrated a positive correlation (r = 0.34; 95% confidence interval, 0.25 to 0.42; P < 0.001). We calculated sensitivity, specificity, positive (PPV) and negative predictive value (NPV) for the ability of 24HUC thresholds to predict calcium malabsorption. When low calcium absorption was defined as <120 mg/d, a 24HUC value <150 mg demonstrated 65% sensitivity, 67% specificity, 31% PPV, and 89% NPV. When calcium malabsorption was defined as <100 mg/d, a 24HUC value <150 mg demonstrated 72% sensitivity, 65% specificity, 22% PPV, and 94% NPV. A 24HUC value <150 mg demonstrated a high NPV for calcium malabsorption. We suggest that 24HUC levels can exclude calcium malabsorption in postmenopausal women.