Greg Grunberg Reveals Sudden Baldness Is Due to Alopecia Diagnosis Following Surgery

The actor also shared that he lives with Hashimoto’s disease.

Greg Grunberg attends the Los Angeles Premiere of Max Original Series "Duster" in Universal City, Calif., on May 8, 2025. Monica Schipper/Getty Images

Actor Greg Grunberg, known for his roles in “Felicity,” “Heroes,” and “Alias,” is speaking out about his recent hair loss after being diagnosed with alopecia, an autoimmune disorder that causes the body to attack its own hair follicles.

In a YouTube video posted on May 7 to his “Talk About It” channel, Grunberg addressed public concern over his altered appearance after photos circulated of him without his usual hair.

“First of all, I want to thank everybody who’s asking if I’m okay,” he said. “Well, this is what’s happening.”

He then removed his hat to reveal his bald head. “I, all of a sudden, got alopecia, and I knew nothing about it. I’m still learning about it.”

Grunberg, 58, believes the condition may have been triggered by a knee replacement surgery he underwent in October 2024.

“I think it shocked the alopecia into, you know, actually presenting itself,” he said. “I think I probably had it dormant in my body for a long time.”

The actor also disclosed he has Hashimoto’s disease, a thyroid-related autoimmune condition. The combination of that and his post-surgery pain medication, he speculated, could have exacerbated the onset of alopecia.

According to the Cleveland Clinic and the National Institute of Diabetes and Digestive and Kidney Diseases, both alopecia and Hashimoto’s are linked to immune system malfunctions and can contribute to hair thinning or loss.

Despite the diagnosis, Grunberg maintained an upbeat tone. He said that after searching online, he learned that “millions of people” have the condition. “And I look good!” he added.

Grunberg emphasized that his health is otherwise stable.

He noted that his decision to go public aligns with the mission of his “Talk About It” platform, which encourages open dialogue.

“It would be hypocritical for me not to talk about it,” he said. “Everybody’s got something.”

Greg Grunberg attends "Charlie Hustle & The Matter of Pete Rose" World Premiere in Los Angeles, Calif., on July 10, 2024. Jon Kopaloff/Getty Images for HBO

Grunberg now joins a list of public figures who have shared their experiences with alopecia, including actress Jada Pinkett Smith, who spoke about the condition in 2018, and Riverdale star Lili Reinhart, who posted about her diagnosis earlier this year on TikTok.

According to the Cleveland Clinic, approximately 7 million Americans live with some form of alopecia. While there is no cure, treatments are available, and some individuals experience remission.

“This is the new look you’re going to see,” Grunberg told his fans.