OBJECTIVE: Several studies have suggested that lipoproteins generated during the post-prandial phase are highly atherogenic, with modifications in low-density lipoproteins (LDL) size and density. In the present study we assessed post-prandial variations in LDL size and subclasses in patients with growth hormone deficiency (GHD). DESIGN: We studied in 12 hypopituitary patients with GHD and 10 healthy control subjects matched for gender, age and body mass index (BMI) post-prandial variations after a standardized meal consisting of 35% fat, 45% carbohydrate and 20% of protein (Clinutren Mix, Nestlé) and containing calories corresponding to 1/3 of estimated basal metabolic rate. Blood samples were collected at baseline and after 2 and 4h to measure plasma lipids and LDL size and subclasses by nondenaturing polyacrylamide gradient gel electrophoresis. RESULTS: At baseline patients had similar plasma lipids than controls, with the exception of higher triglycerides (1.2+/-0.8 vs. 0.7+/-0.4mmol/L, p=.0024). Baseline LDL size was similar between the two groups and LDL subclass analysis revealed a small increase in LDL-IIIA (p=.0046). During post-prandial phase no significant differences were found in LDL size and subclasses in patients vs. controls with the sole exception of increased levels of LDL-IVB after 2h (p=.0295) and LDL-IIIB after 4h (p=.0478). CONCLUSIONS: It is, therefore, unlikely that a post-prandial variation in levels of small, dense LDL may significantly contribute to the atherogenic potential in hypopituitary patients with GHD.