I've been trying to put together a case report on the use of testosterone replacement therapy (TRT).
Many references note to the well known side effect of TRT of testicular atrophy.
Sources note that treatment should be stopped if/when testicles decrease to a size of 5 ml's or less.
I wasn't sure how to measure or even estimate this. I was more accustomed to thinking in terms of testicular size in regards to cm's.
Thankfully, it appears that a Swiss pediatric endocrinologist Andrea Prader came up with an orchidometer, or Prader's balls, in 1966 to help clinicians.
It's a string of wooden or plastic balls that vary from 1 ml to 25 ml's used to help estimate testicular size.
It's also been called an "Endocrine Rosary."