This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Androgenic activity of the 19 noestosterone nucleus is decreased by ? 
Select and explain. 
A. Adding alkyl group at C 17, B. Removal of methyl group at C 19, C. Adding methyl group at C 18, D. Substituting chlorine atom at C21
B: Removal of methyl group at C 19
Answer: B: Removal of methyl group at C 19 
Explanation: Ans. is 'b' i.e., Removal of methyl group at C 19Substitution of a 7a-methyl group in 17b-hydroxyestr-4-en-3-one (19-noestosterone) or its 17a-methyl derivative enhanced the androgenic activities of the parent compounds as well as their ability to bind to b protein and to prostate cell nuclei. Thus, 7a, 17a-dimethyl-19-noestosterone had an apparent affinity for bprotein several times higher than that of 5a-dihydrotestosterone.