Endocrine Abstracts

Context: Postmenopausal osteoporosis (PMO) is associated with other comorbidities such as cardiovascular disease and impaired glucose homeostasis. Vitamin D insufficiency is highly prevalent, and may be a common link between these disorders. Recently, it has been shown that vitamin D may be involved in insulin resistance; however, this relationship has not been well evaluated in women with PMO.

Objective: To assess the relationship between circulating levels of 25-hydroxyvitamin D (25OHD) with parameters of glucose homeostasis in a cohort of women with PMO. Additionally, the threshold of 25OHD serum concentration was determined, from which influence at glucose homeostasis were observed in our study population.

Design and methods: Cross sectional study including 40 non obese women with PMO belonging to the coverage area of San Cecilio University Hospital in Granada (Spain). Clinical, anthropometric, bone mineral density and, biochemical parameters related to glucose metabolism (HbA1c, insulin, glucose homeostasis model [HOMA2-Calculator]) and mineral metabolism (25OHD, infracarboxylated osteocalcin [ucOC]) were determined. A descriptive analysis and a multiple linear regression analysis (significance <0.10) was performed.

Results: Mean values of the characteristics of the study population: age 62±8.5 years; BMI 25.4±3.9 kg/m²; percentage of body fat (PBF) 33.9±6.9%; lumbar spine T-score −2.9±0.6 SD; femoral neck T-score −1.8±0.7 S.D.; 25OHD 42.9±19.8 ng/dl; HbA1c 5.4±0.3%; ucOC 8.3±10 ng/ml. Circulating levels of 25OHD were related to glucose metabolism parameters: negatively with HOMA2-IR (R=−0.314, P=0.07), HOMA2-%B (R=−0.468, P=0.003) and insulin levels (R=−0.332, P=0.06); and positively with HOMA2-%S (R=0.368, P=0.02); resulting in an indicator of insulin resistance independently of age, BMI, PBF and ucOC. The patients with serum 25OHD ≥45 ng/ml showed lower values on HOMA2-IR and HOMA2-%B indexes, lower insulinemia, and greater HOMA2-%S index.

Conclusions: Our results support the hypothesis that circulating 25OHD levels are related to glucose homeostasis and therefore constitute a modifiable cardiovascular risk factor in women with PMO.