PTH and vitamin D deficiency: In line with our findings, a prospective study of 494 postpartum women in Canada suggested that vitamin D deficiency/insufficiency with PTH in the highest tertile at 3 months postpartum was associated with worsening β-cell function and insulin sensitivity and increased fasting and 2-h glucose 9 months later, after controlling for age, ethnicity, family history of type 2 diabetes, previous gestational diabetes, BMI, glucose, duration of breast-feeding, physical activity, and season of blood draw [21].