The Problem Came Before the Business Plan
At 27, McCall McPherson was already a practicing physician assistant. She was also, by her own account, spending 16 hours a day flat on her back. She had gained weight, was losing hair, felt depressed, and could not think clearly. Her doctor ran a single lab, told her the thyroid was fine, suggested she eat less and exercise more, and — as McPherson recalled — wanted to reduce her dose while handing her a cholesterol prescription.
'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,' McPherson told Fortune.
That drive home became the origin story for Modern Thyroid Clinic, a telehealth practice headquartered in Bee Cave, Texas.
From $2-Per-Call Answering Service to Eight Figures
McPherson launched the clinic as a one-woman operation — clinician, scheduler, and medical assistant — paying a single phone answerer $2 per call. Today the company employs close to 40 people, operates in 48 states, and McPherson expects it to bring in lower-mid eight figures in revenue this year. The company landed on the Inc. 5000 in both 2025 and 2026, and McPherson made Inc.'s Female Founders 500 list in 2025.
Every dollar of that was self-funded. Until a few months ago, McPherson had never spent a dollar on marketing. Growth came entirely through word of mouth on thyroid advocacy platforms after early patients spread the word.
The Market Gap She Identified
The numbers behind the opportunity are significant. The American Thyroid Association estimates 20 million Americans have some form of thyroid disease. One woman in eight will develop a thyroid disorder during her lifetime, and women are five to eight times more likely than men to be diagnosed with a thyroid condition, according to the ATA. The ATA also estimates up to 60% of people with thyroid disease do not know they have it — McPherson believes the real figure is closer to 80% or 90%.
Her clinical argument is straightforward: nearly 90% of thyroid patients in the U.S. are placed on levothyroxine, a synthetic version of the inactive T4 hormone, and left there. Many patients, she contends, cannot efficiently convert T4 into the active T3 hormone their bodies actually use. Modern Thyroid Clinic runs a fuller lab panel than a typical primary-care visit and prescribes active thyroid hormone rather than T4 alone. The practice also treats Hashimoto's disease — the autoimmune condition driving most hypothyroidism — as something that can be actively managed rather than simply monitored. Research McPherson cites suggests standard care captures the 'true picture' of a woman's thyroid function less than 4% of the time.
McPherson's own recovery came after months on a waitlist to see a physician who ran more labs and prescribed active thyroid hormone. She got her life back 'pretty quickly,' she said.
One additional staffing detail sets the clinic apart: McPherson hires only women who also have thyroid conditions themselves, on the theory that patients feel more comfortable with practitioners who have lived the same dismissals.
The CEO Times Read
Modern Thyroid Clinic is a clean case study in what free enterprise does when a regulated, one-size-fits-all medical system leaves patients behind. McPherson did not wait for a federal task force or an insurance mandate. She identified a gap, put her own capital at risk, and built a business that now serves patients across 48 states — without a single marketing dollar for most of its life.
The market has already voted. When a self-funded telehealth startup reaches eight figures on word of mouth alone, it is telling the conventional medical establishment something it has not been willing to hear. Capital rewards clear rules and real results — and in this case, the results walked out of bed.
