Aging and declining testosterone: past, present, and hopes for the future

J Androl. Nov-Dec 2012;33(6):1111-8. doi: 10.2164/jandrol.112.017160. Epub 2012 Aug 9.


As men age, serum testosterone (T) levels decline, whereas serum luteinizing hormone (LH) levels increase somewhat or remain unchanged. Age-related reductions in T levels may be associated with alterations in body composition; energy level; muscle strength; physical, sexual, and cognitive functions; and mood. The predominant contributor to the decline in serum T levels is the decreased ability of the aging testes to make T. As in humans, the Brown Norway rat demonstrates age-related reductions in serum T levels in the setting of unchanged or modestly increased serum LH levels. In this rat model, the ability of aged Leydig cells, the terminally differentiated T-producing cells of the testis, to produce T in response to LH stimulation is significantly diminished. This review begins with a discussion of what is known of the molecular mechanisms by which T synthesis declines with Leydig cell aging. It concludes with a brief history of T replacement therapy, current guidelines, controversies related to T replacement therapy in older men, and proposed future clinical directions.

Publication types

  • Review

MeSH terms

  • Adult
  • Aged
  • Aging / physiology*
  • Animals
  • Hormone Replacement Therapy
  • Humans
  • Hypogonadism / drug therapy
  • Leydig Cells / drug effects
  • Leydig Cells / metabolism*
  • Luteinizing Hormone / blood
  • Luteinizing Hormone / physiology
  • Male
  • Middle Aged
  • Rats
  • Rats, Inbred BN
  • Testis / drug effects
  • Testis / physiology*
  • Testosterone / biosynthesis
  • Testosterone / blood*
  • Testosterone / deficiency
  • Testosterone / therapeutic use


  • Testosterone
  • Luteinizing Hormone