Serum insulin-like factor-3 reveals the long term testicular damage of steroids use
Years after male steroids users renounced their pharmacological muscle enhancers, their testes are still not functioning properly. The concentration of serum insulin-like factor-3, an anabolic hormone about which we still know very little, makes it clear how long lasting the endocrinological impact of a steroid cycle may be. This is evident from a Danish study, in which 132 bodybuilders participated.Study
The researchers, a group of endocrinologists from the University of Copenhagen, studied a group of 132 men aged 18-50 who worked out with weights. These men fell apart into 3 other groups of approximately the same size.

One group had never used steroids, a second group was on a steroids cycle during the study and the third group had used steroids in the past. The average study participant in this group had stopped using anabolics 32 months ago.
The Danes measured the concentration of serum insulin-like factor-3 in the men's blood. That hormone, which in itself also has anabolic properties, is produced by the testes. Endocrinologists suspect that testes are healthier as they produce more serum insulin-like factor-3, and even think that serum insulin-like factor-3 says more about testes' vitality than testosterone.

Of all groups, the men who used anabolics during the study had the lowest concentration of serum insulin-like factor-3 in their blood.

However, the men who had used steroids in the past also had less serum insulin-like factor-3 in their blood than the never users. The never users had an average of 0.59 micrograms serum insulin-like factor-3 per liter, the former users 0.39 micrograms per liter.
The longer the ex-users had been cycling in the past, the less serum insulin-like factor-3 was in their blood.
Click on the figures below for a larger version.

The figure above is also remarkable. You look at the association between the passage of time after the last administration of steroids on the one hand and the concentration of serum insulin-like factor-3 on the other.Well, association... There was no association - which suggests there was no recovery either.
"It is still debated whether illicit use of anabolic steroids causes long-lasting testosterone deficiency", said lead author Jon Jarlov Rasmussen in a press release. [, March 9, 2021.] "Our results suggest a long-lasting impaired gonadal capacity in previous anabolic steroid users."

"The results raise the question whether some previous anabolic steroid users should receive medical stimulation therapy to increase Leydig cell capacity in the testicles."
Rasmussen is thinking of treatment with aromatase inhibitors and SERMs. Sounds familiar.
J Clin Endocrinol Metab. 2021 Mar 9;dgab129. doi: 10.1210/clinem/dgab129. Online ahead of print.