McCall McPherson's Journey from Misdiagnosis to a $400 Million Thyroid Clinic

McCall McPherson, at 27 and practicing medicine, was on a drug nearly 90% of thyroid patients in the U.S. rely on, when she found herself spending 16 hours a day in bed. She'd come home from work at 3:30 p.m. and lie flat on her back through the evening. Weekends were the same. She'd gained weight, was losing hair, felt depressed, and couldn't think clearly. 'Literally, I did not get out of bed,' she told Fortune. 'My life was a constant chase of, well, I have to rest enough to recover for the day and rest enough to prepare for tomorrow.'

A Physician's Struggle with Self-Diagnosis

McPherson sought to adjust her medication with her doctor, who conducted a single lab test, declared her thyroid fine, and advised her to eat less and exercise more. The doctor wanted to reduce her dose and handed her a cholesterol prescription for an issue her thyroid was quietly causing. 'I cried in the car on the way home and thought, If he takes anything else away from me, I will not be a functioning member of society,' she said.

The Birth of Modern Thyroid Clinic

This experience became the foundation for Modern Thyroid Clinic, a telehealth practice based in Bee Cave, Texas. Initially, McPherson was the clinician, scheduler, and medical assistant, paying a single phone answerer $2 per call. Today, she employs nearly 40 people, operates in 48 states, and expects her company to bring in lower-mid eight figures in revenue this year. Modern Thyroid Clinic has also landed on the Inc. 5000 in both 2025 and 2026, and McPherson made Inc.'s Female Founders 500 list in 2025.

The Prevalence of Thyroid Diseases and Modern Approaches

McPherson's approach challenges the conventional thyroid care model, which she argues misses most of the picture and is paid for by women. The American Thyroid Association estimates 20 million Americans have some form of thyroid disease, with one woman in eight developing a thyroid disorder during her lifetime. Women are also five to eight times more likely than men to be diagnosed with a thyroid condition.

Redefining Thyroid Treatment

Modern Thyroid Clinic redefines thyroid treatment by running a more comprehensive lab panel than a typical primary-care visit and prescribing active thyroid hormone (T3) rather than T4 alone. The clinic also treats Hashimoto's disease, the driver of most hypothyroidism, as manageable rather than just monitorable.

The Clinic's Unique Approach

What sets Modern Thyroid Clinic apart is that it hires only women who also have thyroid conditions. McPherson theorizes that patients will feel more comfortable with practitioners who have experienced the condition themselves and have been dismissed elsewhere. 'At that moment, I realized I'm not doing the right thing,' she said. 'This is my calling.'

Future Ambitions

McPherson aims to expand her clinic but has a larger ambition: to make her clinic unnecessary. 'Thyroid is the orphan child. It's just left out in the cold,' she said. 'My hope is that what we do will become the standard of care.'

The widespread prevalence of thyroid diseases in the U.S. and the ineffectiveness of standard treatments are driving the growth of innovative approaches like Modern Thyroid Clinic. Such initiatives present a significant opportunity to enhance healthcare quality and improve patients' quality of life.