CAMBRIDGE — When he tweets, stocks tumble. And biotech executives quake.

Often angry, always skeptical, Adam Feuerstein may be the most feared journalist covering the biotech industry. He delights in deploying careful scientific analysis to take down companies that he believes overhype their drugs, distort their data, or make ridiculously grandiose promises.

And then he takes to Twitter to have a little fun. Feuerstein has blasted companies for peddling nothing more than “diluted bleach water.’’ In his telling, a biotech chief executive is a “liar’’ and a financial analyst a “moron.’’ A top public relations executive is a “human oil slick.’’ Another PR firm? “Idiots.’’ And there’s lots more that can’t be printed.

“I have an itchy trigger finger on hypocrisy,’’ Feuerstein told STAT over beer at Lord Hobo, his favorite bar here, a stone’s throw from the biotech hub of Kendall Square.

His reporting makes waves: Galena Biopharma fired its chief executive after Feuerstein reported that the company had paid outside firms to promote its stock while insiders made millions selling it. At the now-defunct BioPure, an executive landed in jail after Feuerstein reported on safety concerns about the company’s blood substitute. And long before most people had heard of controversial entrepreneur Martin Shkreli, Feuerstein reported that Shkreli’s employees at the biotech firm Retrophin were controlling anonymous Twitter accounts promoting the company’s stock.

There are dozens of examples of a stock dropping, or jumping, in apparent response to Feuerstein’s articles and tweets over the years, according to a STAT review of the archives of StreetAccount, a service that alerts investors about the latest financial market news.

Feuerstein, 48, grew up on Long Island, N.Y., and majored in political science at Emory University. He got his start in professional journalism while still in college, doing a six-month internship at an Atlanta business publication. He kept showing up for work for weeks after the internship ended, until he got hired.

In 2001, Feuerstein landed at the financial website TheStreet, which had a reputation for edgy, aggressive reporting on financial news. Except for a two-year stint as a biotech stock analyst, he’s been there ever since.

Feuerstein is at his desk just after 5 most mornings, working from a spare bedroom in his home near Boston, where he lives with his partner and their two teenagers.

A longtime senior columnist for TheStreet, Feuerstein does occasionally get things wrong, particularly when he tries to predict whether a drug will get approved. One company even put out a string of press releases attacking his reporting as naive and ill-informed.

But investors read him. So does the rest of the biotech world.

“Everyone is keeping an eye on what he covers — all of them,’’ said Dan Budwick, a media strategist at Pure Communications who works with biotech companies.

Indeed, for a guy who writes dense articles that often require a whole lot of Googling to unpack, Feuerstein has a huge following: He has 50,000 Twitter followers and on a good month can get close to a million page views for his articles, an eye-popping total for a journalist writing about a niche subject in a trade publication.

His clout inspires fear.

STAT requested interviews with more than three dozen current or former biopharma chief executives whose publicly traded companies Feuerstein has covered. Some of their PR managers burst into laughter at the very idea that they’d allow an executive to go on the record about a journalist who takes such delight in skewering both companies and individuals.

“You’re taking on an 800-pound gorilla,’’ one said.

Only four CEOs — three of whom periodically drink beer with Feuerstein at Lord Hobo — agreed to talk about him on the record.

The assessment from Nick Leschly, CEO of Bluebird Bio: If Feuerstein thinks you’re spinning him, he’ll “eat you alive.’’ (Leschly, whose company has been the target of a couple mild Feuerstein barbs, made a point of adding that he respects Feuerstein’s reporting.)

His critics complain that Feuerstein attacks companies without first listening to what they have to say. They also whisper, without evidence, that he must be trying to drive down stocks for personal gain. (He says he holds no individual stocks, other than in his publication.)

Pointing to the voluminous record on social media, critics also call him mean.

His boss doesn’t mind all the barbs he flings on social media. “This isn’t summer camp. It can be a rough business,’’ said Jeffrey Kanige, editor in chief of TheStreet. He called Feuerstein’s work “scrupulously fair.’’

For all his acerbic anger online, Feuerstein comes across as warm in person. He can be surprisingly bullish on the biotech industry. And he’s not afraid to show his soft side now and again.

He tenderly chronicled in tweets his dog Max’s months-long battle with cancer. And he has expressed sympathy on Twitter for patients with rare and terrible diseases.

But most of what he writes has a definite edge.

When the biopharmaceutical firm MannKind appointed its now-late founder Alfred Mann as interim CEO last fall at the age of 90, Feuerstein called it “elder abuse.’’ He excoriated Christoph Westphal, the founder of a company developing a treatment for leg cramps made of extracts of ginger, cinnamon, and a derivative of pepper, as the industry’s “Arctic ice-cube salesman.’’

And he isn’t shy about stating — without evidence — that companies are intentionally spinning data or hyping anecdotes to goose their stock.

Asked if it was possible some of those misleading corporate claims could be attributed to an honest mistake, Feuerstein said, “It’s also possible that a pink unicorn will knock on my door tomorrow and offer to make me pancakes. Possible. Just really unlikely.’’

Feuerstein has been harangued and threatened by investors who don’t like his reporting.

But people who know Feuerstein say he’s whip-smart, able to critique study data with a sophistication unmatched by many specialists.

Using those skills to call out hype is Feuerstein’s bread and butter.

Take IsoRay Medical, a small biotech company in Washington that caught Feuerstein’s eye last year when it trumpeted “outstanding results’’ from a retrospective study on 272 early-stage lung cancer patients, some of whom got a radiation therapy developed by the company. IsoRay’s press release claimed 100 percent of patients who got that treatment were still alive five years later. Investors were jubilant; by day’s end, the company’s stock price had doubled.

Feuerstein smelled red meat. When he read the journal article, and compared it with IsoRay’s press release, he found discrepancies.

In a scathing column, Feuerstein accused IsoRay of being “lazy with the facts,’’ playing “rope-a-dope’’ with the data, and “using clever, selective editing’’ in its communications to boost its sagging stock price.

Feuerstein’s reporting infuriated investors, drove down the stock — and sparked more than a dozen class action lawsuits on behalf of investors.

IsoRay’s former and current CEOs both declined requests for interviews.

Rebecca Robbins can be reached at rebecca.robbins@statnews.com Follow her on Twitter @rebeccadrobbins.