Amazon has hired a top cardiologist as it broadens its involvement in the health care industry.

Maulik Majmudar, who is also associate director of the Healthcare Transformation Lab at Massachusetts General Hospital, announced on Twitter that he is moving to "an exciting and challenging role @amazon."

Majmudar did not specify what his job at Amazon (AMZN) would be. The tech giant mostly has kept quiet about its foray into health care.

Neither Majmudar nor Amazon immediately returned request for comment.

Amazon announced in June that it is buying the online pharmacy PillPack, which has pharmacy licenses in all 50 states. The company delivers drugs to customers in pre-sorted doses designed to make it easier for people to take multiple medications a day. The move could accelerate Amazon's long-rumored move into the pharmaceutical business.

Earlier this year, the retail titan teamed up with Berkshire Hathaway (BRKA) and JPMorgan Chase (JPM) to reduce the health care costs of the companies and their employees. The venture, which has yet to be named, hired renowned surgeon and writer Atul Gawande as CEO.

The retailer also has rolled out a line of private label over-the-counter medicines, and is building a business selling a wide array of medical supplies to doctors, dentists and hospitals. The company has a team working on developing employee health clinics, too, according to CNBC.

Majmudar has long worked at the intersection of health care and technology. The Healthcare Transformation Lab says it looks to "improve the experience and value of healthcare for patients and providers through collaborative innovation." It also focuses on digital health, including mobile and wearable devices and data analytics.

Majmudar, who earned his medical degree at Northwestern University, is also a lecturer and visiting scientist at the Massachusetts Institute of Technology and an assistant professor at Harvard Medical School.

He is also medical adviser at Biofourmis, a start up focusing on monitoring patients remotely, and HiLabs, which focuses on health care data mining. He previously served as founding member and chief clinical officer at Quanttus, which unsuccessfully tried to develop a wrist-based app that monitors blood pressure.

1/ Very emotional day: After decade of medical training (@NorthwesternMed @HopkinsMedicine @BrighamWomens), five years on the faculty @MGHMedicine and @harvardmed, leading #digitalhealth @mgh_htl, I have decided to leave academia to take on an exciting & challenging role @amazon — Maulik Majmudar, MD (@mdmajmudar) August 20, 2018

4/ The one and only reason I am taking on this opportunity, is the possibility of making a truly meaningful impact on the health and wellbeing of hundreds of millions of individuals throughout the world... — Maulik Majmudar, MD (@mdmajmudar) August 20, 2018

He is leaving all that behind to focus on Amazon, but his tweet suggests the company has big, global plans.

"The one and only reason I am taking on this opportunity is the possibility of making a truly meaningful impact on the health and wellbeing of hundreds of millions of individuals throughout the world," he tweeted.