Biomarkers of Bone Turnover and Vitamin D Status in Adolescent Girls with Chronic Low Dietary Calcium Intake in Bauchi State

Calcium nutritional rickets and subclinical osteomalacia in Nigerian adolescent girls represent a significant but underrecognized public health problem, driven by chronically low dietary calcium intake rather than vitamin D deficiency, and their biochemical characterisation in Bauchi State fills a critical evidence gap. This study assesses biomarkers of bone turnover and vitamin D status in adolescent girls with documented chronic low calcium intake in rural and urban areas of Bauchi State. One hundred and fifty adolescent girls aged twelve to seventeen years were enrolled: seventy-five with dietary calcium intakes confirmed below 300 milligrams per day by three-day weighed dietary record, and seventy-five with calcium intakes above 500 milligrams per day as controls. Biochemical assessments covered serum calcium, phosphorus, alkaline phosphatase, parathyroid hormone (PTH), 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, osteocalcin as a bone formation marker, and urinary deoxypyridinoline as a bone resorption marker. Results show a pattern of calcium-deficient rickets biochemistry in the low-calcium group: normal or low serum calcium, low-normal phosphorus, significantly elevated ALP and PTH, and significantly elevated 1,25-dihydroxyvitamin D. Notably, 25-hydroxyvitamin D was not significantly different between groups, distinguishing calcium deficiency rickets from vitamin D-deficient rickets. Osteocalcin was elevated in the low-calcium group, indicating increased bone formation turnover. Urinary deoxypyridinoline was also significantly elevated, suggesting concurrent resorption. The biochemical profile provides clear evidence for calcium nutritional rickets as distinct from vitamin D deficiency rickets in this population. Keywords: bone turnover biomarkers, dietary calcium deficiency, rickets, vitamin D, Bauchi State.