The answers to your questions are fairly obvious. If the compound aromatizes, interacts with the estradiol receptor, then there will be an effect on prolactin secretion. The same effects would be expected in a "healthy" person taking AAS. The abstracts above address the questions directly. The estradiol produced from testosterone in TRT will "overpower" the negative dopamine agonist effect of cabergoline, therefore the use of an aromatization inhibitor.
An overview of the regulation of prolactin secretion. Prolactin secretion is paced by a light-entrained circadian rhythm, which is modified by environmental input, with the internal milieu and reproductive stimuli affecting the inhibitory or stimulatory elements of the hypothalamic regulatory circuit. The final common pathways of the central stimulatory and inhibitory control of prolactin secretion are the neuroendocrine neurons producing prolactin inhibiting factors (PIF), such as dopamine (DA), somatostatin (SST), and gamma-aminobutyric acid (GABA), or prolactin releasing factors (PRF), such as thyrotropin releasing hormone (TRH), oxytocin (OT), and neurotensin (NT).
PIF and PRF from the neuroendocrine neurons can be released either at the median eminence into the long portal veins or at the neurointermediate lobe, which is connected to the anterior lobe of the pituitary gland by the short portal vessels. Thus lactotrophs are regulated by blood-borne agents of central nervous system or pituitary origin (alpha-melanocyte stimulating hormone) delivered to the anterior lobe by the long or short portal veins. Lactotrophs are also influenced by PRF and PIF released from neighboring cells (paracrine regulation) or from the lactotrophs themselves (autocrine regulation).
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Direct effects of neurotransmitters, neuromodulators, and peripheral hormones on the activity of tuberoinfundibular dopaminergic system (TIDA). The inhibitory agents (left) will promote an increase of prolactin secretion as a result of diminishing TIDA activity. On the other hand, the stimulatory neurotransmitters and progesterone (right) will tend to decrease prolactin secretion as a result of increasing output of TIDA neurons.
It should be noted, however, that many of these agents have multiple levels of action, often with opposing biological effect. Therefore, in some cases (*), effects on PRF and/or directly at the lactotrophs will prevail over the influence on TIDA activity.
Key: 5-HT, serotonin; NE, norepinephrine; HA, histamine; EOP, endogenous opioid peptides (endorphin, enkephalin, dynorphin, nociceptin/orphanin); GAL, galanin; SST, somatostatin; CCK8, cholecystokinin-8; GABA, gamma-aminobutyric acid; NO, nitric oxide; ACh, acetylcholine; TRH, thyrotropin releasing hormone; OT, oxytocin; VP, vasopressin; VIP, vasoactive intestinal polypeptide; PACAP, pituitary adenylate cyclase-activating peptide; ANG II, angiotensin II; NT, neurotensin; NPY, neuropeptide Y; CT, calcitonin; BOM, bombesin-like peptides (gastrin-releasing peptide, neuromedin B, neuromedin C); ANP, atrial natriuretic peptides.
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