The most common cause is a prolactinoma, a benign (noncancerous) tumor in your pituitary gland. Medication can be beneficial for patients living with infertility, sexual issues, or bone loss. Prolactin levels can fluctuate throughout the day. If it turns out to be a small prolactinoma or a cause can’t be found, your doctor may recommend no treatment at all.
Furthermore, the identification of other pituitary tumors or processes may have important clinical implications for the patient beyond testosterone deficiency.178 Screening questionnaires are not an appropriate tool to identify candidates for testosterone therapy. Radiation to the brain that exposes the pituitary gland can also result in pituitary dysfunction and low testosterone. In conditions where LH is not produced in normal amounts (hypogonadotropic hypogonadism), testosterone deficiency may also result. With worsening Leydig cell function, there is a reduction in the feedback mechanism resulting in elevation of LH levels (hypergonadotropic hypogonadism).
A second large RCT by Snyder et al.319 used the Functional Assessment of Chronic Illness Therapy-Fatigue scales (range 0-52) in 474 men treated with testosterone for 12 months. Duration of studies and mode of administration did not appear to impact outcomes. If normalized, subsequent serial imaging can be performed in two to five years.
If you notice symptoms like nipple soreness or swelling while on TRT, bring it up to your provider – an estradiol check may be done and appropriate therapy started. Estradiol is not an "enemy" – men need some estrogen for bone health, brain function, and even sexual function (estrogen contributes to libido and erectile function too). On TRT, especially at higher doses or with injectable forms, estradiol levels often increase. One case of testosterone-induced macroprolactinoma growth found that even increasing cabergoline doses didn’t completely suppress prolactin until an aromatase inhibitor was added. However, an interesting observation from some case reports is that dopamine agonists may not always fully counteract testosterone-induced prolactin elevation if the mechanism is via increased estradiol. Indeed, bromocriptine or cabergoline can be used to treat any symptomatic hyperprolactinemia, regardless of cause. In a sense, they can "cure" a case of low testosterone that was secondary to high prolactin.
It’s quite uncommon at the doses for prolactinomas, but patients should be made aware to report any odd changes in behavior or impulse control. Another unusual side effect of dopamine agonists, especially noted in Parkinson’s patients on higher doses, is impulse control disorders (e.g. pathological gambling, hypersexuality). But for over 90% of prolactinoma patients, dopamine agonists do the job.