Sex Differences in Salivary Free Insulin-Like Growth Factor-1 Levels in Elderly Outpatients

Objective Many studies have explored serum insulin-like growth factor (IGF)-1; however, only a few studies have investigated its presence in the saliva. Therefore, this study examined sex-based differences in salivary-free insulin-like growth factor-1 (fIGF-1), salivary growth hormone (GH), serum IGF-1 levels, and serum GH levels in older adults aged ≥60 years. The participants were further divided into <75 years and ≥75 years and examined the differences in the levels of the biomarkers mentioned above based on their sex. Design The participants were 80 regular outpatients (40 men and 40 women) with various diseases, including hypertension, diabetes, and hyperlipidemia. We randomly selected them based on the disease being treated. Men and women were divided into two groups according to age (aged <75 years or ≥75 years) for statistical analysis, including Student's t-test and Pearson's and Spearman's correlation coefficient tests. Results  The analysis of sex differences in salivary fIGF-1 levels in patients aged <75 years showed significantly higher levels in women than in men. Correlation analyses of salivary fIGF-1 levels with salivary GH, serum IGF-1, and serum GH revealed a significant positive correlation of salivary fIGF-1 levels with serum IGF-1 and GH levels in men aged <75 years. In women aged ≥75 years, serum GH levels revealed a significant positive correlation with salivary GH levels and age. Conclusions  The results suggested a higher possibility of the local synthesis of oral IGF-1 in women aged <75 years than in men aged <75 years.