This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Sex-Hormone, Subject name: Pharmacology
Erythropoietin is inhibited by - 
Select and explain. 
A. Estrogen, B. Progesterone, C. Thyroxine, D. Testosterone
A: Estrogen
Answer: A: Estrogen 
Explanation: Ans. is 'a' i.e., Estrogen o Estrogen antagonizes the erythropoietin-augmenting effect of placental lactogen. It inhibits utilization of erythropoietin by the marrow stem cell, and also impairs its production.