DOES INSULIN LIKE GROWTH FACTOR-1 (IGF-1) DEFICIENCY HAVE A “PROTECTIVE” ROLE IN THE DEVELOPMENT OF DIABETIC RETINOPATHY IN THALASSEMIA MAJOR PATIENTS?

Abstract

Objective: This cross-sectional study was designed to give insights into relationship between Insulin-Growth-Factor 1 (IGF-1) levels and diabetic retinopathy (DR) in a sample of  thalassaemia major(TM) patients with insulin dependent diabetes mellitus (IDDM). ?his relation was not previously evaluated, despite the fact that both diseases co-exist  in the same patient. The  study   also  describes the clinical and biochemical profile of the associated complications in TM patients with and without IDDM. 

Design: A population-based cross-sectional study.

Participants:The study  includes 19 consecutive TM patients with IDDM and 31 age- and sex-matched TM patients without  IDDM who visited our out-patient clinics for an endocrine assessment

Methods: An extensive medical history, with data on associated complications and current medications, was obtained. Blood samples were drawn in the morning after an overnight fast to measure the serum concentrations of IGF-1, glucose, fructosamine , free thyroxine (FT4), thyrotropin (TSH) and biochemical analysis . Serologic screening assays for hepatitis C virus seropositivity (HCVab and HCV-RNA) were also evaluated,  applying routine laboratory methods.Plasma total IGF-1 was measured by a chemiluminescent immunometric assay (CLIA) method. Ophthalmology evaluation was done by the same researcher using stereoscopic fundus biomicroscopy through dilated pupils. DR was graded using the scale developed by the Global Diabetic Retinopathy Group. Iron stores were assessed by direct and indirect methods.

Results:Eighteen TM patients with IDDM (94.7 %) and 10 non-diabetic patients (32.2 %) had IGF-1 levels below the 2.5^th percentile of the normal values for the Italian population. The mean serum IGF-1 concentrations were significantly lower in the diabetic versus the non-diabetic TM groups (p < 0.001). DR was present in in 4 (21 %) of 19 TM patients with IDDM and was associated with the main classical risk factors, namely inefficient glycemic control  and duration of disease but not  hypertension. Using the scale developed by the Global Diabetic Retinopathy Group, the DR in our patients was classified as non proliferative diabetic retinopathy (NPDR). Only few numbers of microaneurysms [1-3] were detected. Our data also confirm the strong association of IDDM in TM patients with other endocrine and non-endocrine complications.

Conclusions: These results , although on a small number of patients, suggest a possible ‘protective’ role of low IGF-1 in the development of DR in TM patients