Why Might TRT Cause Testicles to Shrink, and How Can This Side Effect Be Managed?

Reviewed by Garrett Kneese, MD, MPH

Family Medicine

When a man uses testosterone replacement therapy (TRT), the extra testosterone sends a signal to the brain that reduces the natural hormone signals, so the testicles shrink because they produce less testosterone. This side effect can be managed by adjusting the therapy or adding treatments like hCG to help keep the testicles active.

Explanation

TRT gives the body extra testosterone that comes from outside, and the brain notices this and thinks, “We have enough now!” Because of this, the brain stops sending the usual signals (through hormones like LH and FSH) to the testicles to make their own testosterone. When the testicles don’t have to work as hard, they can shrink in size. This shrinkage happens because the body is trying to be efficient by not making more testosterone that it doesn’t need. To manage this side effect, doctors often adjust the dosage of testosterone or add human chorionic gonadotropin (hCG) to the treatment. hCG acts like a signal to the testicles, telling them to keep working and stay the right size. Some treatments may also include periodic breaks or combining other medications so that the natural production of testosterone is supported. This way, a balance can be maintained while still getting the benefits of TRT. Always discuss with your doctor to choose the best plan for you.

(References)

Wang C, Swerdloff RS. Testosterone Replacement Therapy in Hypogonadal Men. Endocrinol Metab Clin North Am. 2022 Mar;51(1):77-98. doi: 10.1016/j.ecl.2021.11.005. Epub 2022 Feb 8. PMID: 35216722; PMCID: PMC8994707.
Bassil N, Alkaade S, Morley JE. The benefits and risks of testosterone replacement therapy: a review. Ther Clin Risk Manag. 2009 Jun;5(3):427-48. doi: 10.2147/tcrm.s3025. Epub 2009 Jun 22. PMID: 19707253; PMCID: PMC2701485.
Grech A, Breck J, Heidelbaugh J. Adverse effects of testosterone replacement therapy: an update on the evidence and controversy. Ther Adv Drug Saf. 2014 Oct;5(5):190-200. doi: 10.1177/2042098614548680. PMID: 25360240; PMCID: PMC4212439.
Miah S, Tharakan T, Gallagher KA, Shah TT, Winkler M, Jayasena CN, Ahmed HU, Minhas S. The effects of testosterone replacement therapy on the prostate: a clinical perspective. F1000Res. 2019 Feb 25;8:F1000 Faculty Rev-217. doi: 10.12688/f1000research.16497.1. PMID: 30828436; PMCID: PMC6392157.

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