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: Pharmacology
Hypothyroidism is caused by which of the following anti-tubercular drug - 
Select and explain. 
A. PAS, B. Ethionamide, C. Cycloserine, D. Pyrazinamide
A: PAS
Answer: A: PAS 
Explanation: Ans. is 'a' i.e., PAS Adverse effects of para-amino salicylic acid (PAS) --> Anorexia, nausea, epigastric pain, rashes, goiter (hypothyroidism), fever, malaise, liver dysfunction, and blood dyscrasias. Adverse effects of ethionamide :Anorexia, nausea, vomiting, abdominal pain, hepatitis, optic or peripheral neuritis, metal disturbances and blood dyscrasias.