Mold and its effect on thyroid health

The thyroid is a butterfly-shaped gland in the lower front of the neck that produces hormones regulating metabolism, heart function, digestion, muscle control, brain development, mood, and bone maintenance. It’s a vital part of your endocrine system — and it’s surprisingly vulnerable to environmental stress.

What mold has to do with the thyroid

So what’s the connection? Mold is a powerful but often overlooked stress that can dysregulate the immune system, especially in someone genetically susceptible to mold. When the immune and gastrointestinal systems are stressed by pathogens like mold, it can lead to autoimmune conditions — including autoimmune thyroid disease (AITD).

One clue that mold might be involved is when someone’s health begins to fall apart after a move. In a 2015 survey of 2,232 people with Hashimoto’s, 20% reported that their health declined after a move¹ — possibly indicating a new mold or environmental-toxin exposure. We also watch for toxic mold in anyone immunosuppressed: Aspergillus, a mold common in food and indoor environments, is a threat to thyroid health, and roughly 20% of those with aspergillosis (where Aspergillus infects body tissue) have the mold infiltrating their thyroid.^1,2

What we see in our practice

Clinically, the patients we see who’ve had mold exposure almost always have thyroid conditions — usually one of three patterns:

That last pattern deserves a closer look. The thyroid makes T4 (mostly) and a little T3 in response to the pituitary’s TSH. Because T4 is inactive, it must be converted to active T3 as it circulates. When we’re ill, reverse T3 (RT3) rises and less T3 is made from T4 — a shift that happens with a cold or flu, but can persist in chronic illness like mold exposure.

This is why medication choice matters. People who are inflamed or ill — including the mold-affected — do not convert T4 to T3 well. Given only a T4 medication, they often don’t do well even if bloodwork looks better on paper: T4 influences TSH, so raising T4 drops TSH, which can mislead a physician into thinking the thyroid has improved — when really only the inactive hormone went up. Instead, mold-exposed thyroid patients often benefit from a combination of T4 and T3, alongside reducing mycotoxin levels and mold exposure.

How mold leads to thyroid disease

In our mold series, we looked at how mold causes immune dysregulation, creating CIRS (Chronic Inflammatory Response Syndrome). Here are specific mechanisms by which mold exposure can lead to thyroid disease:

Other thyroid-disrupting toxins

The thyroid is sensitive to compounds that disrupt healthy endocrine function — mold, but also various chemicals and toxins.^6,7 Organochlorine pesticides have a structure resembling T3 and T4, so they may mimic thyroid hormones and cause dysfunction. High urinary concentrations of BPA and phthalates are linked to altered T3, T4, and TSH, and emerging evidence shows flame retardants also alter thyroid hormone levels and function.⁸

Mold is a thyroid disruptor that can damage this vital gland — and those who already have a thyroid condition may be even more sensitive to a mold exposure. We specialize in working with patients who’ve had mold exposure and those living with thyroid conditions; if you suspect mold may be affecting your thyroid, we can help investigate.