INSULIN-LIKE GROWTH-FACTOR-I DECREASES SERUM LIPOPROTEIN(A) DURING LONG-TERM TREATMENT OF PATIENTS WITH LARON SYNDROME

An increased circulating level of lipoprotein(a) [Lp(a)] is a well-rec ognized risk factor for coronary artery disease. While much remains to be understood about its regulation and physiological functions, we ex plored the effect of recombinant insulin-like growth factor-I (IGF-I) administration on circulating Lp(a) levels in 10 Laron syndrome (LS) p atients (five children and five adults) with inherited IGF-I deficienc y. There was no relationship between pretreatment or posttreatment Lp( a) levels and age and sex of the patients. With IGF-I treatment for 6 to 12 months, there was a significant reduction in Lp(a) (65.7% +/- 15 .5%, P < .0001) from the pretreatment level of 76 +/- 45 mg/L to the p osttreatment level of 29 +/- 26 mg/L. This decrease was dosage depende nt on the IGF-I administered (r = .685, F = 0.708, P = .029) and corre lated more strongly with the dosage ratio of the end to the beginning of treatment (r = .78, F = 12.23, P = .008). The higher the IGF-I dose and the higher the dose ratio, the greater the Lp(a) decrease and the lower the Lp(a) at the end of treatment. In conclusion, we observed a dose-dependent relationship between IGF-I administration and Lp(a) re duction in patients with LS. Further studies are needed to elucidate t he mechanism of the effect, but our findings suggest a possible metabo lic link between these two and shed more light on the regulation of ap olipoprotein(a) [apo(a)] expression. It could also open an avenue for additional therapeutic usage of IGF-I. Copyright (C) 1996 by W.B. Saun ders Company