'It's all about the positive intent for Pakistan against South Africa,' writes Younis in a column for the International Cricket Council.
With 13 wickets from four matches, Amir shares the top wicket-taker's position with Australian Mitchell Starc.
'We've given a medical report to the ICC to prove that he is unfit, and after thorough deliberation they allow us to replace him.'
Playing in his 75th Test, the Indian run-machine did it in style with a classic straight drive to take his team to 214 for four in reply to Australia's 326.
The 29-year-old surpassed fellow Indian batting great Sachin Tendulkar, who first crossed the 10,000-run mark in 259 innings in 2001.
Alex Hales will replace the 29-year-old right-hander who hurt himself while playing football.
Rishabh Pant top scored with 92 after being involved in a 152-run fifth-wicket stand with overnight partner Ajinkya Rahane, who made 80.
Shaw, who became the youngest Indian batsman to score a century on debut in the first West Indies Test in Rajkot, hit 8 fours and 1 six in his 42-ball stay so far.
The former captain's 150-ball 144 with 11 fours and four sixes lifted Bangladesh from a precarious 1-2 in the first over to 261.
Cook broke the record of Australia's Allan Border - another left-handed batsman - for most consecutive Test appearances (153), a figure he has now extended to 158, another tribute to his stamina.