Increased levels of insulin-like growth factor 1 (IGF-1) may also be involved, specifically in its anabolic effects. Studies of MGA in elderly patients who experience weight loss are limited and of poor quality with most showing minimal or no weight gain, with no nutritional or clinically significant beneficial outcomes observed. In patients who take MGA, one in 12 will have an increase in weight. Miscellaneous
Unlike the case of the AR, MGA has no significant affinity for the ER. As such, it does not possess the capacity to directly activate the ER. Furthermore, unlike antiandrogens such as spironolactone and bicalutamide but similarly to cyproterone acetate, there is relatively little risk of indirectly mediated estrogenic side effects (e.g., gynecomastia) with MGA. This is because MGA strongly suppresses both androgen and estrogen levels at the same time. Similarly to the case of the ER, MGA has negligible affinity for the mineralocorticoid receptor (MR), and hence does not possess mineralocorticoid or antimineralocorticoid activity.MGA has been found to dose-dependently increase total and free IGF-1 levels up to a dosage of 120 mg/day. Total IGF-1 levels were described as "profoundly" increased, gradually increasing, significantly by 3 days of treatment, up to a maximum of 2.66-fold by 5 to 6 months of treatment. Free (readily dissociable) concentrations of IGF-1 were increased to a smaller extent, by 1.23–2.15-fold, and were described as increasing "moderately". It was suggested that the increase in IGF-1 levels with high-dosage MGA therapy may explain the anabolic effects of MGA in patients with cachexia.
It is available as a generic medication.In Bangladesh and India, megestrol is marketed under the trade name Megestol by Ziska Pharmaceuticals, Mezest by Beacon Pharmaceuticals, and under the trade name Varigestrol by Laboratorio Varifarma, Argentina. Medical uses
MGA is used mainly as an appetite stimulant to promote weight gain in a variety of situations. When given at very high dosages, it can substantially increase appetite in most individuals, even those with advanced cancer, and is often used to boost appetite and induce weight gain in patients with cancer or HIV/AIDS-associated cachexia. In addition to its effects on appetite, MGA appears to have antiemetic effects. MGA is also used as an antineoplastic agent in the treatment of breast cancer and endometrial cancer. It is significantly inferior to aromatase inhibitors in both clinical effectiveness and tolerability as a second-line therapy for breast cancer after tamoxifen failure. MGA was formerly used in combined oral contraceptives in combination with ethinylestradiol or mestranol, and has been used in a combined injectable contraceptive in combination with estradiol as well.Although it has not been approved for these uses, MGA has been studied and/or used off-label for a variety of indications including menopausal hormone therapy and the treatment of hot flashes, gynecological/menstrual disorders, endometriosis, endometrial hyperplasia, ovarian cancer, prostate cancer, benign prostatic hyperplasia, male breast cancer, and precocious puberty. MGA can also be used to treat pattern hair loss in men, but its side effects generally make it unacceptable for this purpose.Appetite stimulation is achieved with MGA with oral dosages of 400 to 800 mg/day.