Hipoandrogenismo adrenal y testicular en la distrofia miotónica

Abstract

Background Myotonic dystrophy type 1(DM1) is the most common inherited form of muscle dystrophy among adults. The genetic defect causing DM1 is an expansion of a CTG triplet repeat at chromosome 19, encoding a protein kinase named DMPK. Primary male hypogonadism is one of the most frequent endocrine disturbances associated with DM1 but there are controversial data among the levels of SHBG and estradiol in men and androstenedione in both sexes. Objective The purpose of this study was to evaluate gonadal function in men and adrenal function in both men and women with DM1. Patients and methods We studied 25 myotonic dystrophy patients (13 males and 12 females) and 25 sex and age matched normal controls. Morning serum levels of DHEAS and androstenedione were determined in all subjects whereas levels of PRL, FSH, LH, total and free testosterone, estradiol, SHBG, and a GnRH test were performed only in male patients. GnRH test were not performed in control subjects. CTG triplet repeat expansions were quantified by PCR and Southern blot. Results Morning serum levels of DHEAS were significantly decreased (p ≤ 0.001) in DM1 patients of both sexes whereas basal levels of serum androstenedione did not differ between patients and controls. We confirmed the primary male hypogonadism in DM1 and we also observed levels of serum estradiol and SHBG significantly decreased (p < 0.01 in both cases) in male patients. Discussion We suggest that glandular (adrenal and testicular) failure is related to the abnormality of the AMPc dependent-protein kinase caused by the genetic mutation. It is possible that hormonal interactions and other factors related to insulin resistance may have contributed to the enzymatic disturbances causing clinical and laboratory alterations observed in this study.