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

Barry R. Zirkin, Joyce Lisa Tenover

Research output: Contribution to journalReview articlepeer-review

49 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)1111-1118
Number of pages8
JournalJournal of andrology
Issue number6
StatePublished - 2012
Externally publishedYes


  • Hypogonadism
  • Leydig cells

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Reproductive Medicine
  • Endocrinology
  • Urology


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