IGF-I and IGFBP-1 in Relation to Body Composition and Physical Performance in Female Olympic Athletes

Relationship of Testosterone, LH, Estradiol, IGF-1, and SHBG with Physical Performance of Master Athletes

Purpose: The aim of this study was to investigate and compare the levels of luteinizing hormone (LH), testosterone (T), estradiol (ES), sex hormone-binding globulin (SHBG), and insulin-like growth factor 1 (IGF-1) in master sprint (MS) and master endurance (ME) athletes. Additionally, the possible associations between these hormones, body composition, and lipid profile with athletic performance (% of performance in relation to the current world record) were analyzed. Materials and Methods: The participants were all men: (i) 34 MS (51.0 ± 6.8 years); and (ii) 32 ME (51.7 ± 9.4 years). Student's t-tests for independent samples were performed to compare all variables between groups. Results: MS had a significantly higher (p = .008) average IGF-1 (154.78 ± 29.85 ng/mL) when compared to ME (129.92 ± 25.48 ng/mL). Performance was significantly correlated with IGF-1 (r = 0.424). The MS group had a moderately lower body fat than ME athletes (MS 12.54 ± 4.07 vs. ME 14.60 ± 4.12; p = .078; d = 0.503). Conclusions: Thus, strength/power training exercise/sport seems to be more beneficial for obtaining a higher IGF-1 compared to aerobic/distance exercise/sport. In addition, LH, T, ES, and SHBG were similar between the two groups of athletes and were comparable to the reference values of younger adults.

Studies of IGF-I and Klotho Protein in Relation to Anabolic-Androgenic Steroid and Growth Hormone Administrations

It has been suggested to longitudinally monitor Insulin-like growth factor I (IGF-I) as a biomarker for the detection of recombinant growth hormone (GH). Subsequently, it is of interest to understand any confounders of endogenous IGF-I. Herein we have studied if serum IGF-I concentration is affected by the intake of anabolic androgenic steroids (AAS) and the potential connection between IGF-I and klotho protein. Moreover, the usefulness of klotho as a biomarker for recombinant GH intake was assessed in healthy male volunteers. An ongoing administration of AAS did not affect the levels of IGF-I. Klotho protein was ~30% higher in men with an ongoing AAS use compared to those with previous (>2 months ago) AAS use, and the serum klotho protein correlated negatively with luteinizing hormone (LH) (r_s = −0.38, p = 0.04) and follicle stimulating hormone (FSH) (r_s = −0.35, p = 0.05) levels. Serum IGF-I and klotho concentrations showed no correlation in the AAS using population but showed a strong negative correlation in healthy volunteers (r_s = −0.86, p = 0.006). The intake of recombinant GH did not affect the serum concentrations of the klotho levels. In conclusion, IGF-I was not affected by supra-physiological AAS doses in men. Interestingly, an association between AAS intake and serum klotho was seen. The usefulness of klotho as an androgen biomarker warrants further studies, whereas klotho can be discarded as a promising biomarker for GH doping.