TSH Levels & Co. — Understand Your Blood Analysis

The Thyroid Gland — A Small Organ of Great Importance

The thyroid gland is a small, butterfly-shaped gland located at the front of your neck, just below the larynx. Despite its small size, it plays a crucial role in your body, especially in your metabolism.

The thyroid gland produces and secretes two main types of hormones: the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones are essential for your metabolism and have an influence on [1]

• your basal metabolic rate
• your heat production
• the synthesis of proteins and enzymes
• lipolysis (fat breakdown)
• glucose uptake and gluconeogenesis (formation of sugar)
• the heart rate and stroke volume
• the breakdown of cholesterol in the liver
• growth during childhood and brain development
• cognition and mental health
• muscle metabolism

The whole interplay is orchestrated by the pituitary gland, an equally small gland in your brain, through the release of TSH (thyroid-stimulating hormone).

TSH signals to your thyroid gland how much T3 and T4 it should produce, depending on your body's needs.

The Hypothalamic-Pituitary-Thyroid Axis

The thyroid gland is part of the endocrine system that controls the production and regulation of hormones. The thyroid gland, the anterior pituitary gland and the hypothalamus form a complex, self-regulating control circuit known as the hypothalamic-pituitary-thyroid axis.

Thyrotropin-releasing hormone (TRH) from the hypothalamus, TSH from the anterior pituitary gland and T4 work together synchronously in this regulatory circuit to maintain proper feedback mechanisms and homeostasis. [1]

What Are TSH Levels/Thyroid Levels?

Thyroid levels are specific biomarkers that indicate the function of your thyroid gland and the concentration of hormones it produces in your blood. Thyroid levels in your blood are crucial for monitoring the function and health of your thyroid and diagnosing potential dysfunctions. [1]

There are three blood levels that are particularly important when analyzing your thyroid levels.

What Are the Different Thyroid Levels?

TSH Levels (Thyroid-Stimulating-Hormone):

TSH stands for "thyroid stimulating hormone", and is secreted by your pituitary gland. TSH levels regulate the production of the thyroid hormones T3 and T4.

An elevated TSH count can indicate an underactive thyroid (hypothyroidism), while a low TSH level can indicate an overactive thyroid (hyperthyroidism). [2]

• Elevated TSH levels: High TSH levels signals the thyroid gland to produce more T3 and T4, which is typical of hypothyroidism. However, the thyroid gland does not produce enough of these hormones, despite the strong signal.
• Low TSH levels: A low TSH level indicates that the thyroid gland is producing too many hormones (hyperthyroidism). The pituitary gland therefore reduces TSH secretion in order to curb hormone production.

T4 (Thyroxine):

T4 is largely transported inactive in the blood and converted into T3 in the target organs. An abnormal T4 value can indicate various thyroid diseases. [1] [2]

• Elevated T4 level: A high T4 level in the blood indicates an overproduction of thyroid hormones, which is typical of hyperthyroidism. This can be caused by an autoimmune disease such as Graves' disease or benign thyroid nodules.
• Low T4 level: A low T4 level indicates an underproduction of thyroid hormones, which is characteristic of hypothyroidism. This can be caused by autoimmune diseases such as Hashimoto's thyroiditis or iodine deficiency.

T3 (Triiodothyronine):

T3 is the active thyroid hormone and plays a central role in your metabolism. It is mainly produced by the conversion of T4 in the target tissues. It regulates the rate at which the body converts energy from food, influences the heart rate and helps to control body temperature. [2]

T3 is crucial for growth and development and for the function of organs and tissues.

Deviations in T3 levels can also indicate thyroid problems.

• Elevated T3: A high T3 level may indicate hyperthyroidism, especially if the T4 level is normal or only slightly elevated. This may indicate an increased conversion of T4 to T3.
• Low T3: A low T3 level may indicate hypothyroidism. Sometimes this occurs when the thyroid gland not only produces less T4, but the conversion to T3 is also impaired.

How Do Thyroid Hormones Work in the Body?

Thyroid hormones regulate metabolism, influence heart rate and blood pressure, promote growth and development, control body temperature and support the function of the brain, muscles and digestive system. [1]

Metabolism

T3 and T4 accelerate energy metabolism by promoting the conversion of nutrients into energy. This affects the body's weight and energy levels.

An underactive thyroid gland (hypothyroidism), for example, slows down the metabolism and reduces your body's energy consumption. This can lead to weight gain, even if calorie intake and activity levels remain the same. [3]

Heart and Circulation

Thyroid hormones increase the heart rate and the contractility of the heart, which leads to higher blood pressure and better blood flow to the organs.

Body Temperature

Thyroid hormones increase the body's heat production, which helps your body to regulate body temperature.

An overactive thyroid (hyperthyroidism) can lead to hot flushes, for example, as it speeds up the metabolism and increases body temperature. This can lead to increased sweating and sudden feelings of heat. [3]

Brain and Nervous System

Thyroid hormones are crucial for brain development and the nervous system, especially during pregnancy and in the first years of life.

Imbalanced thyroid levels can lead to mood swings, as both hyperthyroidism and hypothyroidism affect brain chemistry and hormone balance. Hyperthyroidism can cause anxiety and nervousness, while hypothyroidism is often associated with depression and increased irritability. [3]

Muscle and Bone Health

Thyroid hormones promote the growth and development of muscles and bones, which is particularly important for children and adolescents.

An underactive thyroid (hypothyroidism) can lead to muscle weakness and muscle wasting, while an overactive thyroid (hyperthyroidism) can contribute to muscle tremors and increased muscle fatigue. [3]

Digestive System

The hormones also support gastrointestinal motility and promote the digestion and absorption of nutrients.

A balanced production of thyroid hormones is therefore essential for optimal functioning of the entire body and directly influences your well-being and quality of life.

How Are Thyroid Levels Determined?

Thyroid levels can be determined by means of a blood thyroid test. In the laboratory, the blood is first centrifuged to separate the blood components. The serum or plasma, which contains the hormones, is then isolated.

The concentrations of TSH, free T4 (fT4) and free T3 (fT3) are precisely determined using special analysis devices and methods such as the immunoassay technique (e.g. ELISA or radioimmunoassay).

The results are then analyzed by laboratory specialists and forwarded to your doctor.

The most important biomarkers are TSH levels (thyroid-stimulating hormone), free T4 (fT4) and free T3 (fT3).

• TSH: Indicates how strongly the pituitary gland stimulates the thyroid gland to produce hormones.
• fT4: Measures the amount of available thyroxine in the blood that is not bound to proteins.
• fT3: Measures the amount of available triiodothyronine in the blood that is not bound to proteins.

In addition to the hormone levels, thyroid antibodies can also be measured to diagnose autoimmune thyroid diseases if they are suspected:

• TPO antibodies (thyroperoxidase antibodies): High levels may indicate Hashimoto's thyroiditis or Graves' disease. [2]
• Tg antibodies (thyroglobulin antibodies): Elevated levels also indicate autoimmune diseases such as Hashimoto's thyroiditis. [2]
• TRAK (TSH receptor antibodies): High levels are typical of Graves' disease and lead to hyperthyroidism. [2]

These antibodies are also determined by means of a special blood test in which the blood taken is tested for these specific antibodies.

What Are Normal TSH Levels?

Normal TSH levels are usually between 0.4 and 4.0 mU/l, but can vary slightly depending on the laboratory and analysis method. Women often have higher TSH levels than men, and these can change during pregnancy. [4]

The normal values for fT4 are 10 - 22 pmol/L 0.8 -1.8 ng/dl) and for fT3 3.5 - 7.8 pmol/L (2.0 - 4.4 pg/ml). [4]

It should be noted, however, that the reference values are somewhat controversial and leading thyroid experts such as Dr. Berndt Rieger or Dr. Simone Koch have long advocated that they should not be set at 4.0 or even higher, but at a maximum of 2.5 mU/l, as otherwise patients with subclinical hypothyroidism (mild hypothyroidism) within this range would be overlooked. A detailed medical history is still an important criterion and patients should always be taken seriously.

What Do High or Low Thyroid Levels Mean?

The TSH values of your thyroid gland make it possible to detect potential or latent hyperthyroidism or hypothyroidism at an early stage, even if the thyroid hormone values in the blood are still within the normal range. [4]

Elevated or decreased TSH levels may indicate an impending thyroid dysfunction. The TSH level is therefore the most important screening parameter for the early detection of thyroid disorders. [4]

• Low TSH levels: A TSH level below the normal range can indicate an overactive thyroid (hyperthyroidism), in which the thyroid gland produces too many hormones.
• High TSH levels: A TSH level above the normal range may indicate an underactive thyroid gland (hypothyroidism), in which the thyroid gland does not produce enough hormones.
• Gender-specific differences: Women tend to have slightly higher TSH levels than men, which is due to hormonal differences. During pregnancy, TSH levels often rise to meet the body's increased needs.

However, there are also autoimmune diseases that can attack the thyroid gland and thus cause imbalances in the hormone balance.

Underactive Thyroid (Hypothyroidism)

High TSH levels often indicate an underactive thyroid (hypothyroidism). This means that the thyroid gland is not producing enough hormones.

Symptoms can include fatigue, weight gain, sensitivity to cold, dry skin and depression. Hypothyroidism is often treated with thyroid hormone supplements to balance hormone levels. [3]

Overactive Thyroid (Hyperthyroidism)

Low TSH levels can indicate hyperthyroidism, in which the thyroid gland produces too many hormones. [3]

Symptoms include weight loss, nervousness, insomnia, increased heart rate and sensitivity to heat. Treatment may include antithyroid medication, radioiodine therapy or surgery. [3]

Hashimoto-Thyroiditis

Hashimoto's is an autoimmune disease in which the immune system attacks the thyroid gland, leading to hypothyroidism. Elevated TSH and low T4 levels are typical. Long-term hormone therapy is often necessary. [3]

Graves' Disease

An autoimmune disease that causes hyperthyroidism. It is characterized by low TSH and high T3/T4 levels. Typical symptoms are bulging eyes (exophthalmos) and an enlarged thyroid gland (goiter). [3]

How Are Fluctuating TSH Levels Treated?

Treatment for thyroid levels outside the normal range varies depending on if your TSH levels are too low or too high.

Treatment for Elevated TSH Levels (Hypothyroidism)

Elevated TSH levels usually indicate an underactive thyroid (hypothyroidism). Treatment often includes

Thyroid Hormone Supplements:

Levothyroxine is a synthetic hormone that replaces T4 and normalizes hormone levels. The dosage is adjusted individually, based on regular blood tests. [3]

Lifestyle Changes:

A balanced diet rich in iodine, selenium and zinc can support thyroid function. [3]

Regular exercise can also help to improve metabolism.

Treatment for Low TSH levels (Hyperthyroidism)

Low TSH levels often indicate an overactive thyroid (hyperthyroidism). Treatment options include:

Medication:

Antithyroid medications such as methimazole or propylthiouracil can reduce the production of thyroid hormones. Beta-blockers to relieve symptoms such as palpitations and tremors may also be prescribed. [3]

Radioiodine Therapy:

Radioactive iodine destroys excess thyroid tissue, reducing hormone production. This often leads to long-term hypothyroidism, which is then treated with levothyroxine. [3]

Surgical Removal of the Thyroid Gland (Thyroidectomy):

Partial or total removal of the thyroid gland is recommended in certain cases of hyperthyroidism when other treatments are not effective. [3]