What does Thyroid Nodules do in the body?

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Thyroid Nodules · this is how the organ is built

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Last updated September 2026

In one pass An ultrasound that finds a thyroid nodule most likely is not showing a bad thing that has grown in you.

Educational content, not medical advice — consult a clinician.

Chapter 1

The thyroid is made of tiny follicles

An ultrasound that finds a thyroid nodule most likely is not showing a bad thing that has grown in you. It is the machine finally seeing this organ as it has always been.

Under a microscope the thyroid is not a solid piece of flesh but millions of tiny spheres packed together. Each one is a follicle, a few tenths of a millimeter across: a ring of lining cells forms the shell, and the center holds a pool of thick colloid. That colloid is a warehouse of finished hormone: follicle cells build a large protein called thyroglobulin, attach iodine to it and store it in the center; when hormone is needed, they take it back in and cut thyroid hormone out of it into the blood. The store lasts about two or three months (Zimmermann 2009). So the building unit of this organ is a sphere.

When a small patch of follicles grows a little more eagerly than its neighbors, it bulges into a lump one or two, or three to five, millimeters across, and the high-frequency ultrasound probes used at today's check-ups have reached exactly that resolution. Once the ruler is as fine as the organ's building unit, you start to see its natural grain. Found does not mean it was ever going to harm you.

Keep a different situation apart: a voice that stays hoarse, swallowing or breathing that becomes difficult, or a nodule that grows noticeably over a short time. Do not wait for the next check-up; see a doctor directly. The full list of warning signs is at the end of the chapter Should you avoid iodine?

Numbers · a finer ruler, and detections double

Put probe resolution next to detection rate and the line is blunt.

That German group: earlier work with a 7.5 MHz probe reported a nodule detection rate of 33%; later someone scanned 635 check-up patients with a sharper 13 MHz probe and found nodules in 68% (Guth 2009).

These are two different groups in two different studies, not the same people swapped onto a new machine, so strictly it cannot rule out the populations simply differing. But the direction is clear: this is not more disease — it is resolution catching up with anatomy.

The same logic holds on the autopsy table: when pathologists section a thyroid finely enough, they find plenty of tiny foci in people never diagnosed in life — and that detection rate has not risen in sixty years (Harach 1985; Furuya-Kanamori 2016). The conclusion is one line — the finer you look, the more you find.

Background · what autopsies find

This organ is natively a heap of millimeter-scale spheres; autopsy data only confirm the same thing from another direction.

Finland (Harach 1985): 101 consecutive autopsies, thyroids subserially sectioned at 2-3 mm. Fifty-two occult papillary carcinoma foci were found across 36 glands — a 35.6% detection rate, the highest reported anywhere at the time. Tumor diameter ranged from 0.15 mm to 14 mm, with 67% under 1 mm. The authors titled the paper accordingly: in Finland, this is a normal finding.

Six-decade pooled analysis (Furuya-Kanamori 2016): 35 studies, 12,834 autopsies. Stratified by examination intensity:

Whole gland examined: 11.2% (95% , CI, 6.7-16.1%: the range the true value most likely falls in)Partial sampling only: 4.1% (95% CI 3.0-5.4%)
The same pooled analysis found that the autopsy detection rate has not risen over six decades.

Why is Finland 35.6% and the pooled figure only 11.2%? Because Finland's section interval (2-3 mm) was far finer than most studies. Notice the coincidence: the blade's interval is in millimeters, and the probe's resolution is in millimeters — both rulers are graduated at exactly the scale at which a patch of follicles bulges into a lump, so they are seeing the same thing.

In other words, a detection rate is a number about your method, not about the disease. And the reason a method can move it at all is that anatomical fact: this organ's grain sits at the millimeter scale to begin with.

Chapter 2

The brain keeps telling it to grow

Your thyroid has not rested since birth, and something has been pushing it the whole time. Pushed for decades, it grows unevenly, which is a thoroughly ordinary result.

The thyroid does not decide how much work to do; that decision sits with the pituitary gland at the base of the brain. The pituitary keeps tasting the level of thyroid hormone in the blood: when it runs low, it releases thyroid-stimulating hormone () into the blood.

TSH drifts through the bloodstream to the neck and settles on receptors on the surface of follicle cells. That one landing does three things at once: it makes the cells pull iodine in from the blood; it makes them take back the colloid in the center and cut hormone out of it into the blood; and it makes the cells taller and more numerous, which is hyperplasia, growth by adding cells.

The first two are the day's work; the third is a long-term account. TSH is not only an accelerator pedal; it is also a growth signal.

The key is the next step. The same TSH washes over millions of follicles, and they do not all respond alike: some grow as soon as they are pushed, others barely react. A year of pushing shows nothing; after ten or thirty years, the few that were ahead pull further and further away, from a spot visible only under a microscope to a lump you can feel or see on a scan.

That is where a nodule comes from. It is not something that got in from outside; it is your own follicles, grown unevenly after decades of pushing.

Mechanism · Why iodine shortage keeps the throttle down

When blood hormone is adequate, the pituitary lifts its foot; when it isn't, the foot stays down.

When iodine is short, that foot never comes up. Not enough raw material, not enough hormone; not enough hormone, so the pituitary keeps releasing ; TSH keeps coming, so follicle cells are driven to proliferate year after year, and the whole gland enlarges — that is goiter (Zimmermann 2009).

And follicles carry innate differences: some are sensitive to TSH and grow eagerly; others barely bother. So two facts that used to be puzzling need no statistics to explain:

Why are nodules so common? Because everyone's thyroid is being prodded, without a break, for life.Why do they multiply with age? Because the longer the prodding runs, the wider the gap opens.
A nodule you can feel or scan has, as its default explanation, this organ's normal way of working — not something in there killing you.

Mechanism · why many, not one

The word "multi" in the diagnosis multinodular goiter comes straight from the differences between follicles: if every follicle answers differently, then after decades of prodding what surfaces is never one lump but a batch of them, in assorted sizes.

Autonomous nodules, also called hot nodules: as they grow, some nodules simply stop taking orders from TSH and make hormone at their own pace. This is especially common in regions with long-standing iodine deficiency — decades of prodding accumulate a set of unsupervised workshops.

Those workshops produce a counterintuitive consequence: when iodine is restored to a long-deficient population, a transient wave of hyperthyroidism appears — iodine-induced hyperthyroidism. The unsupervised nodules suddenly receive ample raw material, run flat out, and overproduce hormone (Zimmermann 2009). This is part of the right-hand half of the U-shaped curve that links iodine to the thyroid.

So could you run it backwards — suppress TSH and shrink the nodule? It's a natural thought: if TSH is the growth signal, cut the signal. That road was tried and rejected. Guidelines explicitly advise against levothyroxine TSH suppression for benign nodules in iodine-sufficient populations, because the benefit doesn't cover the cost — to hold down a lump that most likely won't harm you, you soak your whole body in mild thyrotoxicosis for years, buying arrhythmia and bone-loss risk (American Thyroid Association 2015 guideline, Haugen 2016).

Mechanistically coherent is not the same as clinically worth it.

Chapter 3

Why most of them don't move

Most of these small things in the thyroid stay where they are for years and grow slowly. That holds even for the low-risk microcarcinomas already diagnosed among them: a hospital in Japan measured such patients by ultrasound year after year, and over ten years more than nine in ten did not grow by 3 mm or more.

Why can they stay this quiet? A nodule is a patch of follicles that grew a little more eagerly, and the cancer that grows from follicle lining is classed by pathologists as differentiated thyroid cancer. Differentiated means it still looks a lot like the original follicle cell and still does the original job: it still takes up iodine, still makes thyroglobulin, still listens to . A cell that is still doing its day job divides slowly and has little ability to spread. It is an entirely different thing from the cancer that has completely forgotten what it is (that kind is very aggressive).

So for low-risk microcarcinomas that have been properly assessed, one path is open: do not cut yet, watch with regular ultrasound, and operate if it truly grows. This is active surveillance. It is not a gamble and not giving up on treatment; it keeps surgery for when it is needed, and a doctor decides by set criteria who is suitable for this path.

Anatomy is what makes this possible: the thyroid sits just under the skin at the front of the neck, so ultrasound sees it clearly through one layer of skin, as often as you like. The pancreas and the ovaries are buried deep in the abdomen and get no such treatment.

Clinical · someone actually watched for years

This isn't armchair reasoning; someone spent decades testing it. From 1993, Kuma Hospital in Japan did something brave: it offered patients with low-risk papillary microcarcinoma an extra option — don't cut yet, just watch with periodic ultrasound. That is active surveillance. The low-risk bar is explicit: no more than 1 cm across, not growing outside the capsule, no lymph node metastasis, and not sitting against the trachea or the recurrent laryngeal nerve.

1,235 people were watched this way for years, and the results were (Ito 2014):

Tumors that grew by 3 mm or more: 4.9% at 5 years; 8.0% at 10 yearsNew lymph node metastases at 5 / 10 years: 1.7% / 3.8%Across the whole program, nobody developed distant metastasis and nobody died of thyroid carcinoma
Over ten years, more than nine in ten did not grow by 3 mm or more. And for the under-one-in-ten that did grow, operating once it grew was still in time — the group converted to delayed surgery had no life-threatening recurrences.

Know its limits: this is an observational cohort from one hospital, where patients chose surveillance themselves rather than being randomized. It shows that properly assessed low-risk microcarcinomas can be watched this way, not that every nodule or every thyroid cancer can.

Chapter 4

Why surgery has a cost

"Cut it out for peace of mind." That sentence assumes the cost is zero. The cost is not zero, and the reason is written in the anatomy: pressed against the back of the thyroid are two structures that matter a great deal and are very hard to avoid.

The first is the recurrent laryngeal nerve, which opens and closes your two vocal cords. It runs down the neck, loops around the large blood vessels at the top of the chest, and turns back upward (recurrent means turning back); the returning stretch runs in the groove between the windpipe and the esophagus, and the outer side of that groove is the back of the thyroid. To lift the thyroid out of there, the surgeon has to cut right beside the nerve; injure it, and the vocal cord on that side stops moving well and the voice goes hoarse.

The second is the parathyroid glands: four of them, each the size of a grain of rice, also stuck to the back of the thyroid, guarding the calcium level in your blood. They are tiny, their color is close to the surrounding fat, and their blood supply depends on fine vessels branching off the thyroid's own. So the more common risk is not cutting them out but severing those fine vessels during dissection: the gland stays in place, but starves. Once it stops working, blood calcium drops and your hands and feet start to tingle and cramp.

The typical complications of thyroid surgery are a hoarse voice and tingling hands and feet not because surgeons are careless, but because this is how the back of the organ is built. Every dissection happens right beside these two structures.

Background · this isn't blaming anyone — it's the bill

First, to be clear: this is not blaming anyone. Many people have already had the surgery, and under the consensus of the time their doctors' advice was entirely reasonable. The point isn't that you shouldn't have had it — it's why this bill can never be zero, so that people who haven't reached this fork can weigh both sides on the same scale.

Injure the recurrent laryngeal nerve on both sides and breathing is compromised; that is the heaviest tier.

One more line item you cannot dodge: after part or all of the thyroid is removed, the remaining tissue may not supply the hormone you need, so a daily tablet makes up the difference. That isn't a complication, it's arithmetic — you took part of that hormone warehouse out yourself.

Kuma Hospital's comparison of complications after immediate surgery and during active surveillance comes from one of the highest-volume, best centers in the world for this operation. In the hands of surgeons who do fewer of these operations, complications are usually more common (Adam 2017).

Clinical · What surgery and surveillance each cost

At one hospital, patients with low-risk microcarcinoma chose either immediate surgery or active surveillance; here are the two groups side by side (Oda 2016; not randomized):

Taking levothyroxine (to replace hormone or suppress ): 66.1% vs 20.7%Transient hypoparathyroidism (numb hands and feet, cramping): 16.7% vs 2.8%Permanent hypoparathyroidism: 1.6% vs 0.08%Transient vocal cord paralysis (voice goes hoarse): 4.1% vs 0.6%Permanent vocal cord paralysis: 0.2% in the surgery group, 0 in surveillance
Map these rows onto the anatomy at the back of the gland: the two parathyroid rows are the four rice grains on the back being injured or starved during dissection; the two vocal-cord rows are the nerve climbing back up the tracheoesophageal groove. The menu of complications is set by anatomy — it isn't random bad luck.

Removing only half isn't free either: after hemithyroidectomy, 26.4% of 535 patients ultimately still needed levothyroxine (Ahn 2019). The remaining lobe doesn't always cover it.

Whether the operator does this often matters, concretely: US data show that the lower a surgeon's annual volume, the higher the patient's complication rate — a relationship that continues up to roughly 26 cases per year (Adam 2017). So the numbers above, from an ultra-high-volume center like Kuma, represent this operation's ceiling performance, not its average.

And one line item that never appears on a consent form. Once the word cancer is attached to you it doesn't peel off: in US data, thyroid cancer survivors report psychological financial hardship at nearly twice the rate of other cancer survivors (46.1% vs 24.0%, Barrows 2020). Insurance, mortgages, work, and the few days before every follow-up scan are all in that account.

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Chapter 5

Reading the scan, and when to biopsy

The words on an ultrasound report, hypoechoic, microcalcifications, taller-than-wide, are not mystical scores. Each one stands for a specific look of the tissue under a microscope. What the radiologist is doing is reading histology through the skin.

What they read is echoes: sound waves go in, meet different things, and bounce back stronger or weaker. Take the easiest one: a lump that looks dark on the image means the cells inside are packed tight, with no colloid and no fluid. The warehouse in the center is gone; the cells just grow and no longer do the job of storing hormone. No longer doing its day job looks like this on ultrasound.

Ask that kind of question five times and add up the answers, and you have the American College of Radiology's thyroid ultrasound scoring system, TI-RADS (Tessler 2017). Only after a nodule is graded does the question arise of drawing out a few cells with a thin needle to look at them, which is fine-needle aspiration (FNA). The threshold weighs grade and size together: the lower the grade, the larger the nodule has to be. An 8 mm nodule that looks well behaved is, by the rules, not needled. That is not about saving money or cutting corners: needle it, and what turns up is most likely something this organ always carries and that would never have caused trouble, yet it can push you all the way to the operating table.

So "found a nodule, needle it" is wrong, and "it's only a nodule, ignore it" is also wrong. Stratifying means letting each nodule take the path that fits it.

Mechanism · What each ultrasound feature is asking

This organ is natively a heap of spheres, prodded into growing unevenly; what grows mostly still does its day job; and acting on it carries an anatomical cost. Add those four facts up and you don't get "don't look". You get: we need a way to guess what the cells inside this lump look like, without cutting it open. Ultrasound is that way, and every sonographic feature is an indirect answer to a histological question:

Cystic or spongiform points benign. A lump that looks like a cluster of little bubbles looks that way because that's what it is: swollen follicles, still holding colloid in their centers. Fluid barely blocks sound, so it reads bright. It's that normal structure, enlarged but not distorted.Solid and hypoechoic (dark on the image) points suspicious. To reflect sound you need interfaces. A dark lump means the cells inside are packed shoulder to shoulder with no colloid and no fluid — the warehouse in the center is gone, and the cells only grow, no longer doing the job of storing hormone.Microcalcifications (specks of white) are the most telling one. These pinpoint bright foci often correspond to psammoma bodies under the microscope: concentric little spheres laid down layer by layer as cells that died inside a papillary carcinoma calcify, only tens of micrometers across (Tessler 2017). Benign colloid nodules usually don't make them. So a scatter of white specks doesn't mean the lump is hard — it means a batch of those cells died in there.Taller-than-wide (standing up) points suspicious. One common explanation: a benign nodule grows passively, pushing along the grain of the surrounding tissue, toward least resistance, and gets squashed into a flat, lying-down shape. A malignant one ignores the grain and grows across tissue planes, so on the image it stands up. Its shape isn't merely odd — it isn't obeying the constraints of the tissue around it.Ill-defined or lobulated margins, or growth beyond the gland, points suspicious. A benign nodule usually shuts itself inside a capsule, with a smooth border. A ragged, lobulated margin means it is infiltrating outward with no wall around it.
The rules are the rules: follow up what needs following, biopsy what needs biopsy, remove what needs removing.

Clinical · TI-RADS and FNA thresholds

TI-RADS stands for Thyroid Imaging Reporting and Data System. Below is the American College of Radiology (ACR) 2017 version (Tessler 2017), placed here so you can read it against your own report.

Five scored feature categories:

1. Composition: cystic / spongiform / mixed / solid (solid scores highest)
2. Echogenicity: anechoic / hyper- or isoechoic / hypoechoic / very hypoechoic (darker scores higher)
3. Shape: wider-than-tall / taller-than-wide (standing up scores higher)
4. Margin: smooth / ill-defined / lobulated or irregular / extra-thyroidal extension
5. Echogenic foci: none / large comet-tail / macrocalcification / peripheral rim / punctate echogenic foci (microcalcification)

Sum the five scores to get a level, then combine with maximum diameter to decide the action:

Level	Points	Malignancy risk	FNA threshold	Follow-up threshold
TR1 benign	0	~0.3%	none	none
TR2 not suspicious	1-2	~1.5%	none	none
TR3 mildly suspicious	3	~4.8%	≥ 2.5 cm	≥ 1.5 cm
TR4 moderately suspicious	4-6	~9.1%	≥ 1.5 cm	≥ 1.0 cm
TR5 highly suspicious	≥ 7	~35%	≥ 1.0 cm	≥ 0.5 cm

The thing to catch in this table is the diagonal: at the same size, the more suspicious it looks, the lower the threshold; at the same appearance, the smaller it is, the more you leave it alone. A 1.2 cm TR3 doesn't get biopsied; a 1.2 cm TR5 does. Size alone is never the reason — size plus appearance is.

Two more things worth knowing:

The American Thyroid Association (ATA) 2015 guidelines are a parallel stratification scheme (Haugen 2016) with the same logic and slightly different thresholds. Which one your report uses depends on the hospital.TI-RADS is a communication and triage tool, not a diagnosis. It gives a probability and a next action, not a conclusion. The real conclusion comes from biopsy cytology, plus you and your doctor weighing your age, family history, symptoms, and how anxious you are.
This page is here to help you read your report, not to grade yourself. Executing the stratification is the clinician's job.

Chapter 6

Should you avoid iodine?

"If you have nodules, avoid iodine, switch to non-iodized salt, and stay away from kelp and seaweed." For most people, this widely shared advice has the direction backwards.

Iodine is the raw material for thyroid hormone. Too little iodine, and not enough hormone gets made; too little hormone, and the pituitary keeps releasing ; with TSH coming nonstop, follicles are pushed to multiply and, over the years, grow into nodules (Zimmermann 2009). So a person who already has nodules and deliberately avoids iodine, hoping to shrink them, is pressing that accelerator harder with their own foot.

More iodine is not better either: in population data, nodules are more common at both ends, too little iodine and too much. People who already test positive for Hashimoto's antibodies, who already have an overactive thyroid, or who are about to have an iodine contrast scan should discuss iodine with their doctor individually.

Your nodule most likely did not come from eating iodine, and avoiding iodine will not make it go away. The point is not to stop looking; it is to stratify, following the guidelines with your own doctor. This is science writing, not medical advice.

See a doctor directly, without waiting, if: your voice stays hoarse; swallowing or breathing becomes difficult; a nodule grows noticeably over a short time; it feels hard and fixed and cannot be pushed around; you can feel enlarged lymph nodes in your neck; you had head or neck radiation exposure in childhood; or a first-degree relative has thyroid cancer. These are the signals that genuinely need further investigation — something entirely different from a small nodule found incidentally at a check-up.

Numbers · iodine's U-curve, bad at both ends

Iodine deficiency is itself a classic cause of nodular goiter — that chain is textbook causation, not correlation.

The data agree. Pool 25 cross-sectional studies and over 50,000 people: those with urinary iodine below 100 µg/L are about 30% more likely to have nodules than people with enough iodine. But look at the other end of the curve too: run the continuous dose-response and the whole relationship is a statistically significant U-shape (P for nonlinearity < 0.001) — risk rises at both the deficient and the excessive end, with the low point around 221 µg/L (Lu 2026, pooled cross-sectional, association not causation).

The right-hand half of the U has a mechanism too: when iodine is abundant, the autonomous nodules that no longer take orders from suddenly receive ample raw material and run flat out (Zimmermann 2009). So neither end is good — it is not "less is safer", and it is not "more is better". The iodine-thyroid U-curve is covered in more detail in the Iodine story.

There are two genuine exceptions who should discuss iodine with a doctor individually: people who already test positive for Hashimoto's antibodies (details in the Hashimoto's Thyroiditis story), and people facing iodine contrast imaging or with existing hyperthyroidism.

Myth · Six things people say about nodules

Nodules grow into cancer, so cut it out while it's small

The vast majority of nodules are benign, and benign nodules almost never turn into cancer — histologically they are two different roads. A benign nodule is the normal follicle structure, enlarged, still holding colloid in its centers; a cancer is a follicle cell grown distorted, no longer doing the storage job. They are not two stretches of the same road. As for the ones that really are papillary microcarcinoma, more than nine in ten did not grow by 3 mm or more in ten years (Ito 2014). The benefit of cutting early is imagined as large and the cost as zero; both are wrong.

Thyroid cancer is the lucky cancer — just take it out and you're fine

This makes two errors at once. It prices the surgical bill at zero (the recurrent laryngeal nerve and the four rice grains are pressed against the back of the gland), and it hides the genuinely dangerous minority. Differentiated cancer is mild because it still remembers being a follicle cell; run that backwards and the one that has entirely forgotten is savage — anaplastic carcinoma is only about 1.7% of thyroid cancers, but historical median survival is about 5 months, with 1-year survival of 20% (Bible 2021). Thyroid cancer isn't one disease; it's a group spanning a huge range of differentiation. Calling it lucky is deeply unfair to that minority.

Adding a thyroid ultrasound to the check-up package must be a good thing

Reason from mechanism first: an organ natively grained at the millimeter scale, measured with a millimeter-scale ruler in people without symptoms — you will inevitably find a great deal, and many of those people will be pushed toward the operating table. Which is why, for thyroid cancer screening in adults without symptoms, the US Preventive Services Task Force (USPSTF) grade is D: recommended against, because the harms outweigh the benefits (USPSTF 2017). Read the scope of that USPSTF grade D carefully: it applies to screening people without symptoms. Having symptoms, having a family history, or being told to get checked by your doctor is an entirely different situation — get checked.

Prunella or seaweed goiter pills dissolve nodules

No reliable evidence supports any herb shrinking nodules. There's a historical misunderstanding worth clearing up: classical formulas treated goiter with seaweed and kombu because ancient goiter was mostly iodine-deficiency goiter — and back then, supplying iodine meant releasing the throttle, which genuinely worked. But the nodule a check-up finds today is not the same illness at all; the old remedy is answering a different question.

Worth noting: even the pharmaceutical route isn't recommended. Guidelines explicitly advise against levothyroxine TSH suppression for benign nodules, because the benefit doesn't cover the harm (American Thyroid Association 2015 guideline). If cutting the growth signal doesn't clear the bar even as a drug, an herb certainly doesn't.

Nodules come from anger and bottled-up stress

No reliable human evidence — and mechanistically there's no way in. The growth signal for follicle cells is TSH, and TSH is set by the thyroid hormone level in your blood, not by your mood. The real function of this claim isn't to explain a cause; it's to make people blame themselves, converting an anatomical finding that has nothing to do with your personality into a personal failing.

This logic only applies to the thyroid

No. But what you should take away isn't a statistical rule — it's a set of structural conditions. Any organ that meets three criteria at once will see "found" come apart from "going to harm you":

1. It natively carries a large stock of quiet small lesions (thyroid: follicles prodded by TSH for decades)
2. Most of those lesions still do their day job and grow slowly (differentiated)
3. There is a cheap, non-invasive test whose resolution is finer than the lesions' scale (a 13 MHz probe against millimeter lumps)

With all three in place, you will find a great deal that was never going to surface. That isn't a statistical curiosity; it's the necessary consequence of those three structural conditions.

Prostate is the closest sibling: the same huge reservoir of indolent lesions, the same cheap test that pulls them up, and the same conditional, shared-decision-making recommendation from the US Preventive Services Task Force (USPSTF 2018). The Benign Prostatic Hyperplasia story covers screening in detail.

The pattern has been quantified for thyroid cancer in women in high-income countries: depending on the country, an estimated 50-90% of diagnoses are overdiagnosis (Vaccarella 2016). But that number is only the scoreboard for those three structural conditions — it is not the starting point of the reasoning. The starting point is the anatomy: this is simply how the organ is built.

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References · 11

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Guth, S., Theune, U., Aberle, J., Galach, A., & Bamberger, C. M. (2009). Very high prevalence of thyroid nodules detected by high frequency (13 MHz) ultrasound examination. European Journal of Clinical Investigation, 39(8), 699-706. 635 check-up patients: nodules in 68% with 13 MHz scanners versus 33% previously reported with 7.5 MHz. 10.1111/j.1365-2362.2009.02162.x
Harach, H. R., Franssila, K. O., & Wasenius, V. M. (1985). Occult papillary carcinoma of the thyroid. A normal finding in Finland. A systematic autopsy study. Cancer, 56(3), 531-538. 101 autopsies sectioned at 2-3 mm; 52 occult papillary carcinoma foci in 36 glands (35.6%), the highest rate reported worldwide. pubmed.ncbi.nlm.nih.gov/2408737
Furuya-Kanamori, L., Bell, K. J. L., Clark, J., Glasziou, P., & Doi, S. A. R. (2016). Prevalence of differentiated thyroid cancer in autopsy studies over six decades: A meta-analysis. Journal of Clinical Oncology, 34(30), 3672-3679. 35 studies, 12,834 autopsies: incidental prevalence 11.2% whole-gland vs 4.1% partial sampling; prevalence did not increase over six decades. 10.1200/JCO.2016.67.7419
Haugen, B. R., Alexander, E. K., Bible, K. C., Doherty, G. M., Mandel, S. J., Nikiforov, Y. E., et al. (2016). 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer. Thyroid, 26(1), 1-133. Recommends against routine TSH suppression therapy for benign nodules in iodine-sufficient populations. 10.1089/thy.2015.0020
Ito, Y., Miyauchi, A., Kihara, M., Higashiyama, T., Kobayashi, K., & Miya, A. (2014). Patient age is significantly related to the progression of papillary microcarcinoma of the thyroid under observation. Thyroid, 24(1), 27-34. Active surveillance of 1,235 low-risk patients: 5- and 10-year enlargement 4.9% and 8.0%; no distant metastasis and no thyroid-carcinoma deaths. 10.1089/thy.2013.0367
Oda, H., Miyauchi, A., Ito, Y., Yoshioka, K., Nakayama, A., Sasai, H., et al. (2016). Incidences of unfavorable events in the management of low-risk papillary microcarcinoma of the thyroid by active surveillance versus immediate surgery. Thyroid, 26(1), 150-155. Immediate surgery vs active surveillance: levothyroxine 66.1% vs 20.7%; permanent hypoparathyroidism 1.6% vs 0.08%. 10.1089/thy.2015.0313
Adam, M. A., Thomas, S., Youngwirth, L., Hyslop, T., Reed, S. D., Scheri, R. P., Roman, S. A., & Sosa, J. A. (2017). Is there a minimum number of thyroidectomies a surgeon should perform to optimize patient outcomes? Annals of Surgery, 265(2), 402-407. Complication likelihood decreased with increasing surgeon volume up to 26 cases per year. 10.1097/SLA.0000000000001688
Tessler, F. N., Middleton, W. D., Grant, E. G., Hoang, J. K., Berland, L. L., Teefey, S. A., et al. (2017). ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White paper of the ACR TI-RADS Committee. Journal of the American College of Radiology, 14(5), 587-595. FNA thresholds 2.5 cm for TR3, 1.5 cm for TR4, 1.0 cm for TR5. 10.1016/j.jacr.2017.01.046
Lu, C., Dong, H., Shi, P., Dong, W., Wen, X., & Gao, Q. (2026). Correlations between iodine status and the risk of thyroid nodules: a systematic review and dose-response meta-analysis. Frontiers in Endocrinology, 17, 1711749. 25 cross-sectional studies, 54,621 participants: nonlinear U-shaped association; iodine deficiency OR 1.28. Cross-sectional design - association, not causation. 10.3389/fendo.2026.1711749
National Institutes of Health, Office of Dietary Supplements. (2022). Iodine — Fact Sheet for Health Professionals. Fact sheet (updated November 5, 2024; Wayback snapshot 16 September 2026): commercial seaweeds range from 16 to 2,984 mcg iodine per gram; dried nori, 2 tablespoons flaked (5 g), 116 mcg; US iodized salt is labelled 45 mcg iodine per gram (measured 47.5-50.7); two RCTs giving 150 or 200 mcg/day iodine from early pregnancy to delivery found no effect on child cognitive, language or motor scores at 1.5-2 years, and one found no benefit at 5-6 years either (fact sheet). ods.od.nih.gov/factsheets/Iodine-HealthProfessional