Prospective Associations of Vitamin D Status with Beta-cell function, Insulin Sensitivity and Glycemia: The Impact of Parathyroid Hormone Status
- Caroline K Kramer1,2,
- Balakumar Swaminathan1,
- Anthony J Hanley1,2,3,
- Philip W Connelly2,4,
- Mathew Sermer5,
- Bernard Zinman1,2,6 and
- Ravi Retnakaran1,2,6⇑
- 1Leadership Sinai Centre for Diabetes, Mount Sinai Hospital, Toronto, Canada
- 2Division of Endocrinology, University of Toronto, Toronto, Canada
- 3Department of Nutritional Sciences, University of Toronto, Toronto, Canada
- 4Keenan Research Centre for Biomedical Science of St. Michael’s Hospital, Toronto, Canada
- 5Division of Obstetrics and Gynecology, University of Toronto, Toronto, Canada
- 6Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Canada
- Corresponding Author: Ravi Retnakaran E-mail:
Previous studies have yielded conflicting findings on the relationship between low vitamin D (25-OH-D) and impaired glucose homeostasis. In this context, we hypothesized that combined assessment of 25-OH-D with its regulator parathyroid hormone (PTH) may be required for optimal evaluation of the impact of vitamin D status on glucose metabolism. Thus, we evaluated the prospective associations of 25-OH-D and PTH at 3-months postpartum with beta-cell function (Insulin Secretion-Sensitivity Index-2 (ISSI-2)), insulin sensitivity (Matsuda index) and glycemia at 12-months postpartum in 494 women undergoing serial metabolic characterization. Notably, 32% of those with pre-diabetes/diabetes at 12-months postpartum had both vitamin D deficiency and PTH in the highest tertile at 3-months postpartum. On multiple-adjusted linear regression analyses, vitamin D deficiency/insufficiency with PTH in the highest tertile at 3-months independently predicted poorer beta-cell function (P=0.03) and insulin sensitivity (P=0.01), and increased fasting (P=0.03) and 2-hour glucose (P=0.002) at 12-months postpartum. In contrast, vitamin D deficiency/insufficiency with lower PTH did not predict these outcomes. In conclusion, only vitamin D deficiency/insufficiency with increased PTH is an independent predictor of beta-cell dysfunction, insulin resistance and glycemia, highlighting the need for consideration of the PTH/25-OH-D axis when studying the impact of vitamin D status on glucose homeostasis.
- Received March 25, 2014.
- Accepted May 20, 2014.
- © 2014 by the American Diabetes Association.
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