Vitamin D increases circulating IGF1 in adults: potential implication for the treatment of GH deficiency

Abstract

Objectives: Previous studies suggested that vitamin D modulates circulating IGF1. We investigated this effect in adults and its clinical relevance in the management of GH deficiency (GHD). Design and methods: IGF1 levels were prospectively measured before and after 12 weeks of treatment with oral vitamin D 3 (5000 or 7000 IU/week) vs no intervention in 39 subjects 61.9G7.9 years old. The frequency of IGF1 values R50th age-and sex-specific percentile in relation to vitamin D status, as determined by the concentration of 25-hydroxyvitamin D (25(OH)D), was retrospectively assessed in 69 GHD patients (57.4G16.6 years) on stable hormone replacement and with 25(OH)D and IGF1 concurrently measured. Results: Treatment with 5000 and 7000 IU vitamin D 3 /week significantly raised 25(OH)D by 12.7G8.4 and 13.1G6.5 ng/ml respectively (both P!0.001 vs baseline). In the 7000 IU group, IGF1 levels also significantly increased by 31.3G36.7 ng/ml (PZ0.01). Neither 25(OH)D nor IGF1 significantly varied in controls. IGF1 was R50th percentile more frequently in GHD patients with 25(OH)D levels R15 than !15 ng/ml (65.9 vs 40.0%, P!0.05). Logistic regression with adjustment for recombinant human GH (rhGH) dose, vitamin D supplements, gender, use of thyroid hormones, corticosteroids or estrogen/testosterone, and season revealed a significant positive association between R15 ng/ml 25(OH)D and IGF1 R50th percentile (OR 4.4, 95% CI 1.0-18.8, P!0.05). A significant negative correlation between 25(OH)D concentrations and rhGH dose was found after correcting for age and IGF1 (b K0.042, P!0.01), but not after further adjusting for sex, thyroid, adrenal or gonadal replacement, and season (b K0.037, PZ0.06). Conclusions: Vitamin D increases circulating IGF1 in adults. As a result, a better vitamin D status may ease the achievement of normal IGF1 values in GHD.

Hyperglycemia Promotes Schwann Cell De-differentiation and De-myelination via Sorbitol Accumulation and Igf1 Protein Down-regulation

“…D 3 levels and are up-regulated in sera by vitamin D 3 treatment (24). Interestingly, we found that expression of Igf1, which encodes a factor that maintains tissue homeostasis (30), was significantly down-regulated in sciatic nerves and clonal Schwann cells under high glucose conditions but that its expression was rescued by either ARI or vitamin D 3 treatment (Fig.…”

“…Insulin-like growth factor 1 (Igf1) is similar to insulin in structure and function and regulates various aspects of growth and development of individuals (23). Igf1 is produced primarily in the liver following growth hormone stimulation (23), and vitamin D 3 level is reportedly correlated with serum Igf1 levels (24).…”

Testicular Synthesis and Vitamin D Action

“…Based on cross-sectional studies in community-based cohorts, positive correlations of vitamin D and IGF-I have been observed (36,37). Ameri et al (38) showed that vitamin D increased circulating IGF-I levels in adults and speculated that a better vitamin D status can favor the normalization of IGF-I levels in adults with treated GH deficiency.…”

Vitamin D across growth hormone (GH) disorders: From GH deficiency to GH excess

“…In addition, the concentration of 25OH-D3 was retrospectively assessed in 69 GHD patients on stable hormone replacement. The authors demonstrated higher IGF-I levels in GHD patients with higher 25OH-D3 levels (≥ 15 ng/ml), and a logistic regression analysis confirmed a significant positive association between ≥15 ng/ml 25OH-D3 levels and higher IGF-I [22]. Confirmatory data in healthy populations were collected by Bogazzi et al, who identified a positive relationship between serum 25OH-D3 and IGF-I concentrations in 241 healthy subjects [23], and by Hippönen et al in a large population of 6810 British adult subjects [6], concluding that 25OH-D3 status may contribute to determining serum IGF-I levels.…”