INSULIN-LIKE GROWTH FACTORS (IGFS) AND IGF-BINDING PROTEINS (IGFBPS) IN ELDERLY CHINESE, CORRELATION WITH OTHER ENDOCRINE AND METABOLIC CHANGES

Abstract

Previous studies have described serum profiles of insulin-like growth factor-I (IGF-I), -II (IGF-II), and IGF binding protein-3 (IGFBP-3) in elderly populations and reported an age-associated decline in serum IGF-I, but these studies have been mainly in Caucasian populations. For comparison and to set up a baseline database for the elderly population of ethnic Chinese in Singapore, the present study investigated serum IGF profiles, in association with dehydroepiandrosterone-sulfate (DHEA-S), sex hormones, thyroid hormones, and lipid profiles, in a group of elderly community dwelling ethnic Chinese men and women in Singapore (aged 60-99 years) who were all ambulatory, some who had no known illness ('healthy' group, n = 64), and some with various chronic illnesses ('unhealthy' group, n = 53). Healthy young ethnic Chinese acted as controls (n = 30). As expected, in healthy elderly Chinese, serum levels of total IGF-I, total IGF-II, IGFBP-3were significantly lower than in healthy young controls (p < 0.05). There was a further significant decline in serum IGF-I levels after 60 years old in the healthy group (p < 0.05). Unhealthy elderly Chinese had a significantly lower serum IGF-I level compared to healthy elderly Chinese (p < 0.001), and their already very low serum IGF-1 levels did not decline any further after 60 years old. The adrenal hormone, DHEA-S, also declined with ageing, and was significantly correlated with serum IGF-I in the healthy elderly population (r =0.38, p < 0.002). However, serum DHEA-S did not differ between the two elderly groups. Both groups of elderly men had a comparable serum total testosterone level as the young controls. No correlations were found between serum IGFs and serum total testosterone or serum thyroid hormones. Healthy elderly Chinese women had a higher serum total cholesterol level than the young controls (p < 0.05) whereas healthy elderly men had a similar level as the young controls. Healthy elderly Chinese had significantly higher Lp(a) levels than the young controls (p < 0.05). Unhealthy elderly Chinese had lower serum total cholesterol and Lp(a) levels compared to healthy elderly Chinese (p < 0.05). In conclusion, serum IGF-I, total cholesterol and Lp(a) levels were significantly lower in the unhealthy group, and thus may be associated with the disease morbidity of ageing, whereas serum PSA, DHEA-S and the other measurements did not show the same correlation with disease morbidity, but correlated with increasing age alone. These findings may have some implications on the direction of future studies, especially on therapeutic interventions, which attempt to reduce the morbidity associated with ageing.