Interesting tidbit about why stopping Cyproterone for monotherapy can cause adverse effects despite adequate levels

"Through its action as a progestogen, CPA has been found to significantly increase prolactin secretion and to induce extensive lobuloalveolar development of the mammary glands of female rhesus macaques.^([109]) In accordance, a study found that CPA, in all cases, induced full lobuloalveolar development of the breasts in transgender women treated with the medication in combination with estrogen for a prolonged period of time.^([110])^([111])^([112]) Pregnancy-like breast hyperplasia was observed in two of the subjects.^([112]) In contrast, the same study found that men with prostate cancer treated with a non-progestogenic antiandrogen like flutamide or bicalutamide and no estrogen produced moderate but incomplete lobuloalveolar development of the breasts.^([110]) Based on the above research, it was concluded by the study authors that combined estrogenic and progestogenic action is required in transgender women for fully mature female-like histologic breast development (i.e., that includes complete lobuloalveolar maturation).^([110])^([111]) Also, it was observed that lobuloalveolar maturation reverses upon discontinuation of CPA after surgical castration, similarly to the case of mammary gland involution in postpartum women, indicating that continued progestogen treatment is necessary to maintain the histology.^([110])^(")