Shooting Blanks? It May Be the Tamoxifen

Effect of chronic administration of Tamoxifen on fertility in male bonnet monkeys (Macaca radiata).

Researchers: Rao AJ, Ramachandra SG, Ramesh V, Krishnamurthy HN, Jayaraman S, Gopalakrishnan K, Juneja HS

Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore, India.

Source: Andrologia 1998 May-Jun;30(3):129-32

Summary: Administration of Tamoxifen via the Alzet pump at a rate of 50 micrograms hr-1 for 90 days in the adult male bonnet monkeys Macaca radiata had no effect on the serum testosterone concentration determined at 10 AM and 10 PM as well as total sperm count determined at 15-day intervals over a period of 260 days. However, a significant reduction in sperm motility was observed beyond 90 days up until the 225th day. Breeding studies conducted from day 90 to 260 revealed that these males were infertile.

Discussion: Tamoxifen, or Nolvadex, is classified as an antiestrogen. I’m sure most of you are already familiar with this drug. It works as an antiestrogen by competitively binding to estrogen receptors. Although it has high affinity for estrogen receptors it has little if any estrogenic effects in most tissues. It is used by bodybuilders to prevent or treat gynecomastia and water retention. The interesting thing about this study was the fact that Tamoxifen, an antiestrogen, made the male monkeys infertile. This is in agreement with another recent study looking at the effects of an aromatase inhibitor (Steroids 1998 Jul-Aug;63(7-8):414-20) on fertility also in male monkeys. Both of these studies point to an important role of estrogen in male fertility. Tamoxifen, unlike the aromatase inhibitor which caused a 2-10 fold increase in serum testosterone levels, showed no effect on serum testosterone. The effect on spermatogenesis was clearly due to estrogen. Their sperm count was fairly normal, however, the sperm couldn’t swim to save their own lives. The take home message is that if you want to start a family between shows, stay away from Nolvadex and Proviron. On the other hand, these two compounds may be potential male birth control remedies. I guess the glass is either half full or half empty depending on how you look at it.