title: Vitamin D increases circulating IGF1 in adults: potential implication for the treatment of GH deficiency.
abstract: OBJECTIVE
  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).
  
  
  METHODS
  IGF1 levels were prospectively measured before and after 12 weeks of treatment with oral vitamin D3 (5000 or 7000 IU/week) vs no intervention in 39 subjects 61.9±7.9 years old. The frequency of IGF1 values ≥50th 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 (57.4±16.6 years) on stable hormone replacement and with 25(OH)D and IGF1 concurrently measured.
  
  
  RESULTS
  Treatment with 5000 and 7000 IU vitamin D3/week significantly raised 25(OH)D by 12.7±8.4 and 13.1±6.5 ng/ml respectively (both P<0.001 vs baseline). In the 7000 IU group, IGF1 levels also significantly increased by 31.3±36.7 ng/ml (P=0.01). Neither 25(OH)D nor IGF1 significantly varied in controls. IGF1 was ≥50th percentile more frequently in GHD patients with 25(OH)D levels ≥15 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 ≥15 ng/ml 25(OH)D and IGF1 ≥50th 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 (β -0.042, P<0.01), but not after further adjusting for sex, thyroid, adrenal or gonadal replacement, and season (β -0.037, P=0.06).
  
  
  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.
authors.affiliation: Internal Medicine Unit, Department of Internal Medicine, Centre of Excellence for Biomedical Research, IRCCS-AOU San Martino-IST, University of Genova, Viale Benedetto XV, 6, 16132 Genova, Italy.
authors.forename: Pietro
authors.initials: P
authors.lastname: Ameri
authors.forename: Andrea
authors.initials: A
authors.lastname: Giusti
authors.forename: Mara
authors.initials: M
authors.lastname: Boschetti
authors.forename: Marta
authors.initials: M
authors.lastname: Bovio
authors.forename: Claudia
authors.initials: C
authors.lastname: Teti
authors.forename: Giovanna
authors.initials: G
authors.lastname: Leoncini
authors.forename: Diego
authors.initials: D
authors.lastname: Ferone
authors.forename: Giovanni
authors.initials: G
authors.lastname: Murialdo
authors.forename: Francesco
authors.initials: F
authors.lastname: Minuto
mesh_terms: D000368:Aged; D005260:Female; D020249:Hormone Replacement Therapy; D019382:Human Growth Hormone / Q000097:blood* / Q000172:deficiency*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007558:Italy; D016014:Linear Models; D016015:Logistic Models; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D016896:Treatment Outcome; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000188:drug therapy*; D014815:Vitamins / Q000008:administration & dosage / Q000097:blood / Q000627:therapeutic use*
chemical_list: D014815:Vitamins; D019382:Human Growth Hormone; D014807:Vitamin D; D007334:Insulin-Like Growth Factor I; C104450:25-hydroxyvitamin D