Thyroid: When to Check Symptoms and Lab Values?

Thyroid diseases are common, and women are affected considerably more often than men. Many people learn about an unusual value by chance; others search for a long time for an explanation of tiredness, feeling cold or inner restlessness. This article explains in general terms what the thyroid does, which biochemical pathways lie behind it, what is known about causes and when a medical check is important.

Why the thyroid? What is known about causes

In the individual case the cause is often not clear. For the common autoimmune forms, research assumes an interplay: an inherited predisposition, which by estimates accounts for the larger part of the risk, and triggers from the environment. Named factors include iodine supply, selenium and vitamin D, infections, certain medications, pregnancy, smoking and stress (review, Biomedicines 2024). How strongly each factor acts is supported by evidence of varying quality.

In holistic medicine we do not look at the thyroid in isolation. From the practice’s experience, a thyroid disorder often appears together with a shift in the whole metabolism: nutrient supply, inflammatory processes, the gut and persistent emotional strain. This is a view drawn from accompanying many people, not a proven model. It explains why we take time for the whole system rather than looking at a single value.

Biography and strain: the question “Why me?”

After a diagnosis, many people ask why it is happening to them now. In a large Swedish study with more than 100,000 people, autoimmune diseases occurred more often in people with stress-related disorders than in comparison groups and in their siblings (Song et al., JAMA 2018). The study shows an association, not a cause.

That is why one point matters to us: nobody is to blame for a thyroid disease. In our sessions it can still help to look at life phases, burdens and turning points. Not to force an explanation, but to understand what shapes everyday life today and where relief is possible.

What the thyroid does in the cell

The active hormone T3 acts in almost every cell of the body. It binds to receptors in the cell nucleus and switches on genes there, including those for energy metabolism. It also acts on the mitochondria, the power plants of the cell. In this way T3 helps set the basal metabolic rate, the energy the body uses at rest: for heat, heartbeat, digestion and the work of the organs (review on energy expenditure, review on T3 in mitochondria).

Put simply: with too little T3 the cell runs on a low flame, with too much at full speed. Many of the symptoms further down follow from this.

Cascade 1: from phenylalanine to adrenaline

Tyrosine is the shared building block. It gives rise to the stress messengers and, within the protein thyroglobulin, to the thyroid hormones. These also influence how sensitively the body responds to adrenaline.

Phenylalanine → tyrosine

hydroxylase, BH4

Tyrosine → L-dopa

BH4, iron

L-dopa → dopamine

vitamin B6

Dopamine → noradrenaline

vitamin C, copper

Noradrenaline → adrenaline

SAMe

Cascade 2: tyrosine, iodine, T4, T3 and reverse T3

The thyroid mainly produces T4, the storage form. It becomes active when one iodine atom is removed: this produces active T3 or inactive reverse T3. More in our article on reverse T3.

Iodine

building block of the hormones

Selenium

conversion of T4 to T3

Iron

thyroid peroxidase

More reverse T3

can occur with illness, stress or severe calorie restriction

The feedback loop

When hormone levels in the blood are high, TSH falls. When they are low, TSH rises. That is why TSH is usually the first lab value.

Autoimmune diseases of the thyroid

Hashimoto’s thyroiditis

Usual lab tests: TPO-AK, thyroglobulin antibodies, TSH. In regions with sufficient iodine supply the most common cause of an underactive thyroid.

Graves’ disease

Usual lab tests: TRAK, TSH, fT3, fT4. Can also affect the eyes.

Effects on the body: underactive and overactive thyroid

The symptoms are varied and unspecific and often have other causes too, for example sleep, stress, iron or vitamin B12 (Tired Despite Enough Sleep: Which Lab Values Can Be Checked?).

Iodine and selenium: what studies show

Iodine. Iodine deficiency can lead to goitre and an underactive thyroid (Iodine deficiency: causes and consequences). Too much iodine is not favourable either. In a study in three Chinese regions with different iodine intake, new cases of mild hypothyroidism over five years were more frequent with higher intake (0.2% with mild deficiency, 2.6% and 2.9% with more than adequate and excessive intake), as were new cases of autoimmune thyroiditis (0.2%, 1.0% and 1.3%) (Teng et al., NEJM 2006). An accompanying editorial stressed that the consequences of iodine deficiency weigh more heavily worldwide. Iodine intake therefore belongs in the right range, not as high as possible.

Selenium. A Cochrane review evaluated four studies with 463 people with Hashimoto’s (van Zuuren et al., Cochrane 2013). Selenium lowered TPO antibodies in three studies. The studies were small and methodologically weak, and whether people feel better or need less hormone remained open. Selenium can itself be harmful in high doses. Taking it should therefore be discussed with the treating doctor beforehand.

Which lab values are usual

• TSH: usually the first value, a signal from the pituitary gland.
• fT4 and fT3: the free, active hormones; reverse T3 where needed.
• Antibodies: TPO-AK and thyroglobulin antibodies when Hashimoto’s is suspected, TRAK when Graves’ disease is suspected.
• Ultrasound: a medical examination of the size and structure of the thyroid.

The reference range comes from the laboratory and differs between methods. We do not set our own limits; we show the laboratory’s range and discuss what it can mean in your case. High-dose biotin can distort measurements, and taking thyroid tablets on the day of the blood draw can also play a role. Ask the laboratory or the practice beforehand.

How we proceed at Natura Heilpraxis

We begin with a conversation about symptoms, life circumstances and goals and decide together which values fit the question. You are welcome to bring existing results; we go through them calmly. We do not prescribe prescription-only medication, and thyroid medication is never changed or stopped without medical consultation. An overview of laboratory services is on the page Laboratory Diagnostics, background on metabolic pathways at Understanding Biomarkers and in the freely accessible reference work ORY Biomarker. Our discussion does not replace medical diagnostics.

Sources

• Cyna W. et al.: The Impact of Environmental Factors on the Development of Autoimmune Thyroiditis. Biomedicines 2024. Full text
• Song H. et al.: Association of Stress-Related Disorders With Subsequent Autoimmune Disease. JAMA 2018;319(23):2388–2400. PubMed
• Teng W. et al.: Effect of Iodine Intake on Thyroid Diseases in China. N Engl J Med 2006;354:2783–2793. DOI
• van Zuuren E. J. et al.: Selenium supplementation for Hashimoto’s thyroiditis. Cochrane Database of Systematic Reviews 2013. Cochrane Library
• Mullur R. et al.: Thyroid Hormone Regulation of Metabolism. PMC · Wrutniak-Cabello C. et al.: Thyroid hormone action in mitochondria. J Mol Endocrinol 2001. PubMed