Interactions between vitamin D and IGF-I: from physiology to clinical practice

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• The interplay between vitamin D and insulin-like growth factor-I (IGF-I) occurs at endocrine and paracrine/autocrine levels.
• Vitamin D positively correlates with serum IGF-I and IGF binding protein-3 (IGFBP-3) in healthy individuals.
• IGF-I influences vitamin D metabolism, affecting calcium-phosphate balance and parathyroid hormone (PTH) secretion.

Purpose of the Study:

• To explore the complex interactions between vitamin D and the IGF-I/IGFBP axis.
• To investigate the implications of these interactions for conditions like growth hormone deficiency (GHD) and acromegaly.
• To examine the role of vitamin D and IGF-I in carcinogenesis, particularly breast cancer.

Main Methods:

• Review of existing literature on vitamin D, IGF-I, and IGFBP interactions.
• Analysis of population-based cohort data showing correlations between vitamin D and IGF-I.
• Examination of studies investigating paracrine/autocrine interactions in various tissues and cancer models.

Main Results:

• Vitamin D supplementation increases IGF-I and IGFBP-3, potentially affecting recombinant human growth hormone (rhGH) dosing in GHD.
• IGF-I stimulates renal 1,25-dihydroxyvitamin D production, impacting calcium-phosphate balance and PTH in acromegaly.
• In breast cancer, vitamin D appears to modulate the IGF-I/IGFBP ratio to inhibit proliferation and promote apoptosis.

Conclusions:

• The vitamin D-IGF-I axis has significant physiological and pathological implications, including effects on skeletal and extra-skeletal health.
• Understanding these interactions is crucial for optimizing treatments involving growth hormone and vitamin D.
• Vitamin D's role in modulating the IGF-I/IGFBP ratio suggests a potential therapeutic strategy in certain cancers, like breast cancer.