Your Thyroid and What it Does
Thyroid disorders affect women five to eight times more commonly than men. That's not a minor statistical footnote — that's a condition that is disproportionately common in exactly the demographic most likely to be told their symptoms are stress, depression, or just a natural part of getting older.
And yet the standard approach to thyroid testing in most clinical settings is a single marker — TSH — that tells an incomplete story at best and a misleading one at worst.
I want to give you the full picture. Not because thyroid is an exotic or obscure topic, but because I see the downstream effects of missed thyroid dysfunction regularly in clinical practice — in patients who have spent years on antidepressants, sleep aids, and weight loss programs without ever getting the answer that was sitting quietly in their labs the whole time.
What Your Thyroid Actually Does
Your thyroid is a small butterfly-shaped gland at the base of your neck, and it functions as the metabolic thermostat for your entire body. Every cell in your body has thyroid hormone receptors. That's not an exaggeration — thyroid hormone influences how your heart beats, how your gut moves, how your brain processes information, how your metabolism burns fuel, how your hair grows, how your mood regulates, and how well you sleep.
When thyroid function is optimal, most of these processes run quietly in the background. When it isn't, the symptoms are broad, overlapping, and easy to attribute to almost anything else. That's exactly why thyroid dysfunction goes undetected for so long in so many people.
Why TSH Alone Is Not Enough
TSH — thyroid stimulating hormone — is the signal your pituitary gland sends to your thyroid telling it to produce more hormone. When TSH is high, the pituitary is working harder to stimulate a sluggish thyroid. When TSH is low, the pituitary is backing off because thyroid output is already high.
Here's the problem. TSH is a signal, not a measurement of thyroid output. It tells you what the pituitary thinks is happening — not what your thyroid is actually producing or what your cells are actually receiving.
A patient can have a perfectly normal TSH of 2.0 and still have:
Low Free T3 — meaning the active thyroid hormone is insufficient at the cellular level
High Reverse T3 — meaning the active hormone is being blocked before it can work
Thyroid antibodies — meaning an autoimmune process is attacking the thyroid that hasn't yet moved the TSH out of range
In each of these scenarios, a standard TSH-only panel returns as "normal." The patient is told their thyroid is fine. And they leave without an answer to why they feel the way they do.
The Markers That Tell the Real Story
Free T4 is the primary hormone your thyroid produces. Think of it as the storage form — it circulates in the blood and gets converted into the active hormone when the body needs it. Free T4 tells you how much raw material the thyroid is putting out.
Free T3 is the active form of thyroid hormone — the one that actually enters cells and drives metabolic function. T4 is converted to T3 primarily in the liver, gut, and peripheral tissues. This conversion step is where a significant amount of thyroid dysfunction occurs — and it's completely invisible to a TSH-only panel.
Low Free T3, even with normal TSH and normal Free T4, produces every classic hypothyroid symptom: fatigue, weight gain, cold intolerance, hair loss, constipation, brain fog, slow heart rate, depression, and dry skin. The hormone is being produced — it's just not being converted into the form the body can use.
Reverse T3 is essentially a decoy molecule. When the body is under significant stress — physical illness, chronic psychological stress, prolonged caloric restriction, inflammation — it begins converting T4 into Reverse T3 instead of Free T3. Reverse T3 occupies the same receptors as Free T3 but doesn't activate them. It's a biological brake on thyroid function.
Elevated Reverse T3 explains why some patients with normal TSH and even normal Free T3 still feel hypothyroid. The active hormone is present, but it's being blocked at the receptor level. This pattern is particularly common in women who have been dieting aggressively, dealing with chronic stress, or recovering from illness — and it is rarely looked for in conventional thyroid evaluation.
Thyroid antibodies — TPO and Anti-Tg — are the markers of autoimmune thyroid disease, most commonly Hashimoto's thyroiditis. Hashimoto's is the most common cause of hypothyroidism in the United States, and it can be present for years — causing fluctuating symptoms, immune system activation, and progressive thyroid damage — before TSH ever moves outside the normal range.
Testing for antibodies is one of the most important things I do in a thyroid evaluation, particularly in women with unexplained fatigue, mood instability, or family history of autoimmune disease. Finding elevated antibodies early changes the clinical approach significantly — and gives patients an explanation for symptoms they may have been carrying without a name for years.
The Thyroid-Hormone Connection
One of the reasons thyroid dysfunction is so commonly missed in women is that its symptoms overlap almost perfectly with hormonal changes — and the two conditions are deeply interconnected.
Thyroid hormone directly regulates SHBG — the protein that binds sex hormones and determines how much estrogen and testosterone is available to cells. Low thyroid function raises SHBG, which reduces free estrogen and free testosterone, compounding the hormonal picture significantly. This means that a woman whose estrogen and testosterone levels look adequate on paper may still be functionally deficient because her thyroid dysfunction is keeping SHBG elevated and her sex hormones bound.
Thyroid function also affects the menstrual cycle directly. Subclinical hypothyroidism — thyroid dysfunction that doesn't yet show up as an abnormal TSH — can disrupt ovulation, shorten or lengthen cycles, and worsen PMS and PMDD. It can also affect fertility in ways that aren't caught until someone is struggling to conceive and a more complete evaluation is finally ordered.
Cortisol and thyroid are in constant communication as well. Chronic elevated cortisol — from stress, sleep deprivation, or adrenal dysregulation — directly suppresses the conversion of T4 to active T3 and promotes Reverse T3 production. Which means the same chronic stress that's disrupting sleep and promoting abdominal fat storage is also, simultaneously, slowing thyroid conversion and compounding metabolic dysfunction.
These systems are not separate. Treating one without evaluating the others leaves the picture incomplete.
What Suboptimal Thyroid Function Actually Feels Like
The classic presentation of hypothyroidism — significant weight gain, extremely low heart rate, obvious swelling — represents a relatively advanced state. What most patients experience in the earlier stages is subtler and far easier to dismiss.
If you've been dealing with any of the following without a clear explanation, thyroid function is worth a serious look:
Fatigue that doesn't respond to adequate sleep
Weight that won't move despite genuine effort with diet and exercise
Feeling cold when others around you are comfortable
Hair thinning or increased shedding — particularly from the outer third of the eyebrows
Brain fog, slower thinking, or difficulty with word recall
Constipation or slowed digestion
Low mood or depression that doesn't fully respond to treatment
Dry skin, brittle nails
Morning puffiness, particularly around the eyes and face
A sense of overall slowness — physically and mentally — that used to feel foreign
None of these symptoms are specific to thyroid alone. But when several of them are present together, particularly in a woman in her 30s, 40s, or 50s who has been told her TSH is normal, the thyroid warrants a complete evaluation — not a reassurance based on one marker.
What We Look For at NOVA
When a patient presents with symptoms that could be thyroid-related, I run a full panel — TSH, Free T4, Free T3, Reverse T3, and thyroid antibodies (TPO and Anti-Tg). I also look at the broader hormonal context: cortisol, SHBG, sex hormones, and inflammatory markers. Because thyroid function doesn't exist in isolation, and evaluating it in isolation misses the full picture.
Then we sit down and go through what it shows together. Not just whether the numbers are in range, but whether they're where they need to be for this person to feel well. That distinction matters — and it's the one that conventional thyroid testing consistently fails to make.
If you've been told your thyroid is fine and you still don't feel fine — I'd like to see the full picture. There may be an answer that a single marker missed.
Book a free 30-minute consultation at novawellnessut.com or call and text us at (801) 449-1402. We draw labs right here in the office — no separate lab visit required.
Matt Nelson, NP
NOVA Wellness — Orem, Utah
(801) 449-1402 · novawellnessut.com
