Interactions between vitamin D and IGF-I: from physiology to clinical practice
Pietro Ameri
Clinical Endocrinology 2013 Vol. 79 Issue 1
The interplay between vitamin D and IGF-I is complex and occurs at both endocrine and paracrine/autocrine levels.
Vitamin D has been shown to increase circulating IGF-I and IGFBP-3, with the consistent finding of a positive correlation between vitamin D and IGF-I serum values in population-based cohorts of healthy subjects. The modulation of IGF-I and IGFBP-3 concentrations by vitamin D may impact on recombinant human (rh) GH dosing in the treatment of GHD. It might also underlie some of the extra-skeletal beneficial effects ascribed to vitamin D.
On the other hand, IGF-I stimulates renal production of 1,25-dihydroxyvitamin D, which increases calcium and phosphate availability in the body and suppresses PTH secretion. This effect is responsible for an altered calcium-phosphate balance in uncontrolled acromegaly, and might also account for the improvement in bone metabolism associated with rhGH treatment in patients with GHD.
Data on the paracrine/autocrine vitamin D−IGF-I interactions are abundant, but mostly not linked to one another. As a result, it is not possible to draw a comprehensive picture of the physiological and/or pathological interrelations between vitamin D, IGF-I, and IGF binding proteins (IGFBP) in different tissues. A potential role of vitamin D action is related to its association with carcinogenesis, a paradigm being breast cancer. Current evidence indicates that, in breast tumours, vitamin D modulates the IGF-I/IGFBP ratio to decrease proliferation and increase apoptosis.