OBJECTIVETo analyze the association of the androgen receptor (AR) gene CAG-STR with late-onset hypogonadism (LOH), and explore the pathogenesis of LOH.

METHODSOur investigation involved 1 000 men aged 40-70 years. We randomly selected 127 normal old and middle-aged males and 19 cases of LOH. We detected their levels of Triglyceride (TG), fasting blood glucose (FBG), serum total testosterone (tT) and free testosterone (fT), measured their body mass index (BMI), height, waist circumference (WC) and blood pressure, and examined the length of CAG repeats of the AR gene in the peripheral blood by PCR.

RESULTSThe numbers of CAG repeats ranged from 15 to 32, with a mean value 23.05 +/- 2.95. The mean BMI and FBG were significantly lower (P < 0.01), but TG, tT and fT remarkably higher in the normal than in the LOH men (P < 0.01), while the mean length of (CAG) n repeat polymorphism showed no statistically significant difference between the two groups (22.54 +/- 3.06 vs 23.23 +/- 2.24, P = 0.946). The frequencies of long alleles (n > or = 22) were significantly higher in the LOH than in the normal men (73.68% vs 48.82%, P < 0.05). The numbers of CAG repeats had no significant correlation with tT (r = 0.04, P > 0.05) and fT (r = 0.025, P > 0.05).

CONCLUSIONThe AR gene CAG length showed polymorphism in LOH men. The long alleles (CAG)n (n > or = 22) repeat polymorphism in the AR gene may be a genetic factor for LOH, but it has to be confirmed by further investigation.