High Prevalence of Hypovitaminosis D in Female Type 2 Diabetic Population

doi:10.2337/diacare.24.8.1496

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Letters: Observations
Letter

High Prevalence of Hypovitaminosis D in Female Type 2 Diabetic Population

Giancarlo Isaia, MD¹, Ruben Giorgino, MD, PHD² and Silvano Adami, MD³

¹ Department of Internal Medicine, University of Torino, Torino
² Procter & Gamble Pharmaceuticals, Rome
³ Department of Rheumatology, Ospedale di Valeggio, University of Verona, Verona, Italy

Animal studies have demonstrated lower levels of 1,25(OH)2D3in a type 2 diabetes model compared with controls (1). Alterationsin circulating vitamin D3 metabolites, such as decreased 1 ${alpha}$ -hydroxylaseactivity and enhanced renal 25-hydroxylase activity, have beenfound in both experimental and human diabetes. These alterationsin vitamin D metabolism may be associated with the derangedmineral homeostasis and skeletal morphology observed in ratsand people with chronic insulin deficiency (2). Experimentally,vitamin D deficiency progressively reduces insulin secretion,and this reduction soon becomes irreversible (3). It was alsoshown that insulin deficiency may be associated with lower vitaminD–binding protein and 1,25(OH)2D3 serum levels in rats.These decreases are somewhat dependent on androgen concentration,but they are counteracted by estrogens (4).

Several studies have demonstrated abnormalities in calcium,phosphate, and vitamin D metabolism in diabetic patients. Inparticular, Pietschmann et al. (5) evaluated 25(OH)D levelsin type 1 and type 2 diabetic patients and found no differencein 25(OH)D levels between type 1 diabetic patients and controlsubjects, whereas 25(OH)D levels were significantly decreasedin type 2 diabetic patients (5).

We conducted an observational study in 799 ambulatory postmenopausalItalian women in order to assess the prevalence of hypovitaminosisD and dietary calcium insufficiency. In all patients, the levelsof 25(OH)D3 (obtained by radioimmunoassay method with doubleantibody provided by DiaSorin), calcium intake (obtained bya questionnaire filled in by a general practitioner), and severalActivity Daily Living (ADL) criteria were assessed. The sampleswere collected in February and March 2000.

We identified 66 type 2 diabetic patients based on medical history.Female patients and control subjects were comparable for ageand years since menopause, but BMI was significantly higherin diabetic patients. The ADL score was significantly worsein diabetic patients than in control subjects (P < 0.01).The 25(OH)D levels (means ± SD) were significantly lowerin diabetic patients than in control subjects (11 ± 9.8vs. 9 ± 11.3 ng/ml, P < 0.008), and the prevalenceof 25(OH) deficiency (<5 ng/ml) was significantly higherin diabetic patients than in control subjects (39 vs. 25%).Dietary calcium intake was significantly lower in diabetic patientsthan in control subjects (792.9 ± 400.9 vs. 679 ±316.9 mg/day, P < 0.020).

The significance of these findings remains unclear. The generalrecommendation for overweight diabetic patients to lower fatdairy product consumption may explain the lower calcium intake.We have no data that might explain the higher prevalence ofhypovitaminosis D among diabetic patients. We believe our resultswill lead to additional studies on the hypothetical circularrelationship among diabetes, vitamin D repletion, and calciumintake and absorption. We believe this relationship leads toboth a worsening of diabetes and an increased risk of fractures(6), despite higher bone mineral density levels being foundin diabetic subjects (6,7).

FOOTNOTES

Address correspondence to Giancarlo Isaia, Department of InternalMedicine, University of Torino, Corso Dogliotti 14, 10126 Torino,Italy. E-mail: giancarlo.isaia{at}unito.it.

References

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