Free testosterone and free dihydrotestosterone throughout the life span of men

Objective: The dihydrotestosterone/testosterone ratio seems to be an important factor in the expression of androgenic activity, especially in the prostate and pilosebaceous unit. Whereas the decline of testosterone in aging men is well known, controversial data can be found concerning the age dependence of dihydrotestosterone levels. Hormonal values from our database served for the construction of the life span curve of free dihydrotestosterone/free testosterone ratio. Methods: The results of testosterone, dihydrotestosterone and SHBG determination obtained by immunoassays from 13,152 male patients were used for the calculation of free steroid content and the construction of the age dependence curves. Results: After initial high free dihydrotestosterone: free testosterone ratio in infancy it decreases at the start of puberty and remains practically without change from approx. 20 years of age till senescence. Conclusion: The course of free dihydrotestosterone/free testosterone ratio demonstrates the role of dihydrotestosterone for androgen functions especially in prepubertal age. (C) 2009 Elsevier Ltd. All rights reserved.