In particular, the habitual low calcium intakes of Gambian subjects, leading to secondary hyperparathyroidism [3,7] and potential enlargement of the PTH reserve [32], the relatively high Vitamin D status throughout the year and the high levels of physical activity and low BMI in Gambians compared to African-Americans [9,10] may have influenced these results. The gene discussed is PTH; the disease is secondary hyperparathyroidism.