A plain-language, continually updated guide from Dr. Matt Chalmers’ clinical reference on hormones and peptides.
Your thyroid gland produces two hormones: T4 (thyroxine) and T3 (triiodothyronine). T4 is made in much larger quantities, but it’s really a reservoir — a relatively inactive prohormone that has to be converted into T3 before it can actually do anything. T3 is the active form, and it binds to receptors in virtually every cell in your body to regulate energy production, metabolism, body temperature, heart rate, brain function, and growth.
The whole system runs on a feedback loop: your hypothalamus signals your pituitary, your pituitary releases TSH, and TSH tells your thyroid to make T4 (and a little T3). About 80% of your circulating T3 doesn’t come directly from the thyroid at all — it’s converted from T4 elsewhere in the body, in a process that depends heavily on nutrient status.
Video summary (thyroid and minerals): Thyroid hormone depends on minerals that are often overlooked. Iodine is needed to make thyroid hormone, and selenium, zinc and magnesium are needed to convert T4 into the active hormone T3 and for thyroid hormone to work inside the body’s cells. Research has linked oral contraceptive use with lower levels of some of these minerals, so if you use birth control or have concerns about your thyroid, Dr. Chalmers recommends having your mineral status checked as an early step.
Video summary (what your TSH tells you): Many people are told their thyroid is “fine” based on a TSH and a total T4 alone. TSH is made by the pituitary gland, not the thyroid; it is the signal that tells the thyroid to produce T4 and T3, so it shows only part of the picture. Total T4 includes hormone bound to thyroid-binding globulin, which is inactive. Free T4 and especially free T3, the most active form, show how much hormone is actually available to your cells.
If you have thyroid symptoms despite “normal” results, Dr. Chalmers looks at free T4 and free T3 rather than TSH and total T4. In his view, if your doctor only orders a TSH and a total T4, they are not evaluating thyroid function the right way, and he would not rely on their read, especially if the next step is putting you on medication, because in his experience the vast majority of the time it is a mineral issue. He checks selenium, zinc, magnesium, iodine and, for many women, iron, since low levels can affect how well thyroid hormone works. After correcting low levels for one to two months, retesting shows how you’ve responded. Never stop or change a prescribed thyroid medication without talking with the provider who prescribed it.
“T4 meds like levothyroxine won’t change into T3 or get into the cell without the right amount of selenium, zinc, magnesium and iron… I see lots of women who are on birth control and then all of a sudden they have thyroid or energy issues and no one thought to ask why. It’s not a drug issue, it’s a nutrient issue.”
— Dr. Matt Chalmers, The Pillars Path: A Root-Cause Guide to Hormones, Peptides, and Metabolic Health
Thyroid hormone production runs through five distinct steps in the gland, and nearly every one of them depends on a specific nutrient. Iodine is the literal raw material — T4 and T3 are built by attaching iodine directly onto a tyrosine backbone — but it’s a double-edged sword: too little causes hypothyroidism, while too much can paradoxically shut production down or trigger autoimmune thyroid disease in susceptible people, which is why iodine should be tested before it’s supplemented, not added blindly.
Iron is required by the key enzyme (thyroid peroxidase) that builds the hormone, and low iron stores are one of the most common overlooked causes of low thyroid output, especially in women. Selenium protects the thyroid gland from oxidative damage during hormone production and is separately required to convert T4 into active T3. Zinc, magnesium, and vitamin B12 are all needed just to make the TSH signal that kicks off the whole process in the first place. This is precisely why correcting a nutrient deficiency can resolve thyroid symptoms that look, on the surface, like a medication problem.
Thyroid hormone replacement (levothyroxine/T4 and liothyronine/T3) is FDA-approved prescription therapy for diagnosed thyroid conditions. Evaluation is done through lab testing with our providers.
Levothyroxine (T4) and liothyronine (T3) are FDA-approved prescription therapies for diagnosed thyroid conditions, and thyroid hormone’s documented physiological role includes regulating metabolic rate throughout the body. Appropriateness and dosing are determined through lab testing (not symptoms alone) with our providers.
Some patients don’t convert T4 to T3 efficiently (a process requiring selenium, as noted above) — this is evaluated through lab testing on an individual basis.
This page draws on The Pillars Path: A Root-Cause Guide to Hormones, Peptides, and Metabolic Health by Dr. Matt Chalmers — Pillars of Wellness’ clinical reference on hormone and peptide therapy.
