The medication was introduced for medical use in combination with ethinylestradiol (EE) as an oral contraceptive in 1963 by British Drug Houses in the United Kingdom under the brand name Volidan (4 mg MGA and 50 μg EE tablets), and this was followed by Serial 28 (1 mg MGA and 100 μg EE tablets) and Volidan 21 (4 mg MGA and 50 μg EE tablets) in 1964 and Nuvacon (2 mg MGA and 100 μg EE tablets) in 1967, all by British Drug Houses also in the United Kingdom. It was also marketed under the brand name Delpregnin (5 mg MGA and 100 μg mestranol tablets) by 1965, among others. MGA-containing birth control pills were withdrawn after reports in the early 1970s of a high incidence of venous thromboembolism with the preparations.In the early 1970s, MGA was found to be associated with mammary tumors in beagle dogs, and along with several other progestogens, was withdrawn as an oral contraceptive from several markets including the United Kingdom, Canada, and Germany. It was also under investigation for use as a contraceptive in the United States, but development was discontinued in 1972 following the mammary toxicity findings in dogs, and MGA was never marketed as an oral contraceptive in the United States. Subsequent research, such as monkey studies, revealed that there is no similar risk in humans. Following its withdrawal from the market, MGA was eventually reintroduced for the treatment of hormone-sensitive cancers.
The colorectal adenoma is a benign glandular tumor of the colon and the rectum. It is a precursor lesion of the colorectal adenocarcinoma (colon cancer). They often manifest as colorectal polyps. Comparison table
Tubular adenoma
In contrast to hyperplastic polyps, these display dysplasia. Tubulovillous adenoma
Tubulovillous adenoma, TVA are considered to have a higher risk of becoming malignant (cancerous) than tubular adenomas. Villous adenoma
These adenomas may become malignant (cancerous). Villous adenomas have been demonstrated to contain malignant portions in about 15–25% of cases, approaching 40% in those over 4 cm in diameter. Colonic resection may be required for large lesions. These can also lead to secretory diarrhea with large volume liquid stools with few formed elements. They are commonly described as secreting large amounts of mucus, resulting in hypokalaemia in patients. On endoscopy, a "cauliflower like mass is described due to villi stretching. Being an adenoma, the mass is covered in columnar epithelial cells. Sessile serrated adenoma
Sessile serrated adenomas are characterized by (1) basal dilation of the crypts, (2) basal crypt serration, (3) crypts that run horizontal to the basement membrane (horizontal crypts), and (4) crypt branching. The most common of these features is basal dilation of the crypts. See also
Colorectal cancer
Colorectal polyp


== References ==