OK, I looked at the comments and some I take issue with. Prolactin is not an adult man's friend.
Prolactin actions:
1) acts synergistically with LH to stimulate testosterone secretion from testicles by increasing the number of LH receptors in the testis;
2) influences adrenal androgen formation;
3) enhances testosterone uptake by prostatic cells;
4) alters intra-prostatic androgen metabolism
5) increases uPA to dissolve ECM (extracellular matrix) and facilitate spread of CA
6) enhances angiogenesis
7) decreases libido
8) decreases cognitive function
But the caveat here is that I am a HemOnc and my focus has been prostate cancer and prostate diseases for the last 40 years. So in my context, I like keeping prolactin levels low, very low (e.g., < 10 ng/ml). With TRT, the T ⇢ E2 and the estrogen will increase PRL (prolactin). So I want my adult men to have great cognition, any chance at good libido, and not stimulate PCa (prostate cancer). I have used a lot of cabergoline (Dostinex®) in my medical practice and have found (by checking fasting PRL levels) that often as little as 0.125 mg twice a week (biw) will lower PRL < 10. I also do not want my patients who are on TRT to develop gynecomastia and suppressing estrogen with an aromatase inhibitor and prolactin with cabergoline prevents/solves that problem. So when I use TRT, I monitor PSA to ensure no serial ↑ indicating that an occult PCa has been awoken; I use an AI like anastrozole (Arimidex®) at 0.5 mg biw and titrate the dose based on estradiol (E2) levels, ensure the PRL level is optimal (for my patients < 10) and use cabergoline, but start with 1/2 tab or 0.25 mg biw and lower or raise pending fasting PRL level; I check the DHT level since that is a potent hormone that stimulates prostate growth, which I do not want; and of course, I check the free testosterone which is far more important than total testosterone. I would consider using HCG to preserve the size of the gonads, but in my patient population that is usually not an issue.