Androgen Receptor CAG Repeat Length as a Risk Factor of Late-Onset Hypogonadism in a Korean Male Population

Abstract

Background: Testosterone action is mediated through the androgen receptor (AR), whose sensitivity is influenced by the AR CAG repeat polymorphism. However, the relation between late-onset hypogonadism (LOH) and AR CAG repeat length is unclear and studies of Asian populations are limited. Aim: To investigate the relation between AR CAG repeat length and LOH in Korean men. Methods: 263 Korean men (mean age = 63.43 +/- 10.9 years) were enrolled from 2014 to 2015. LOH diagnosis was based on a serum testosterone level lower than 3.5 ng/mL and positive androgen deficiency according to the Aging Males' Symptom Scale (AMS). Total testosterone levels and answers to the LOH-related questionnaire were analyzed. Outcomes: The relation between AR CAG repeat length and LOH was determined. Results: Mean CAG repeat length was 22.1 +/- 4.6 and mean serum testosterone levels were 2.6 +/- 0.7 and 6.0 +/- 2.0 ng/mL in men with and without LOH, respectively. Men with LOH showed significantly longer AR CAG repeat lengths than men without LOH (26.1 vs 21.6, P < .001). Longer CAG repeat lengths were correlated with higher AMS total scores (r = 0.454, P = .001) and AMS psychotic, somatic, and sexual subscores (r = 0.276, 0.246, and 0.571, P = .006, .007, .001, respectively) and significantly lower 5-item International Index of Erectile Function scores (r = -0.261, P = .001). Multivariate analysis showed that patient age and CAG repeat length were independently associated with LOH (odds ratio = 1.05 and 1.29, P = .041 and <. 001, respectively). Clinical Implications: A longer CAG repeat length is associated with LOH symptoms and LOH. Strengths and Limitations: Associations between CAG repeats and LOH were verified in Korean patients. Moreover, a longer CAG repeat length was shown to be an independent risk factor for LOH. Limitations included the small number of LOH patients studied and that other sex hormone-associated factors were not measured. Conclusions: AR CAG repeat length was associated with LOH prevalence and clinical symptoms in this Korean male population. Thus, it is important to measure CAG repeat length for patients with LOH symptoms with normal testosterone levels. Copyright (C) 2018, The Authors. Published by Elsevier Inc. on behalf of the International Society for Sexual Medicine.