In the present study, using data from the Women’s Health Initiative—Observational Study (WHI-OS), we specifically examined (1) the joint associations of 25(OH)D and PTH with risk for developing diabetes among U.S. white and black postmenopausal women and (2) the joint associations of 25(OH)D and PTH with diabetes-related cardiometabolic comorbidities, including obesity, hypertension, and CKD, among women with diabetes compared to those without diabetes. The gene discussed is PTH; the disease is obesity due to melanocortin 4 receptor deficiency.