In hypothyroidism, the thyroid produces too few hormones (fT3 and fT4). These control the entire metabolism: energy expenditure, heartbeat, body temperature, digestion, mood, skin and hair. When there is a deficiency, everything usually runs on a low flame.³
Hypothyroidism is one of the most common thyroid disorders — women are affected considerably more often than men, and the frequency tends to increase with age.³
The good news
Treatment is usually one of the simplest in medicine — one tablet a day (levothyroxine) replaces the missing hormone. With well-adjusted levels, those affected can usually lead a completely normal life.
2. Causes: Hashimoto's and others
Most common causeHashimoto's thyroiditis — autoimmune disease
The immune system slowly attacks and destroys the thyroid tissue over months to years. Typical antibodies: TPO-Ab and Tg-Ab. At the beginning, in individual cases, even a temporary overactivity can occur (Hashitoxicosis).³
There is a familial clustering. Hashimoto's not infrequently occurs together with other autoimmune diseases: type 1 diabetes, celiac disease, vitiligo.
Other causes
After surgery or radioiodine therapy: When thyroid tissue has been removed or destroyed — e.g. after treatment of an overactive thyroid or a carcinoma. Levothyroxine usually necessary for life.
Medications: Amiodarone, lithium, interferon, certain immunotherapies (checkpoint inhibitors) and tyrosine kinase inhibitors can trigger hypothyroidism. Have thyroid levels checked regularly.
Iodine deficiency: Rare in Germany today thanks to iodized table salt — but still one of the most common causes worldwide.
Congenital hypothyroidism: Rare. In Germany detected in newborn screening and treated immediately.
Central hypothyroidism: Very rare. The problem lies in the pituitary gland (too little TSH) — TSH is then paradoxically low or normal despite reduced fT4.
3. Symptoms
The symptoms usually develop insidiously over months to years and are easily misinterpreted as age, stress or burnout. Many people live for a long time with an unrecognized underactive thyroid.³
Fatigue and listlessness — often the most noticeable symptom; a leaden exhaustion that usually does not improve with sleep
Concentration problems, forgetfulness
Weight gain despite an unchanged diet — due to slowed metabolism and water retention
Sensitivity to cold
Dry skin, brittle hair and nails, diffuse hair loss
Constipation
Depressive mood, listlessness — can be misdiagnosed as depression; with depression, always check the thyroid too
Muscle weakness, muscle cramps, joint pain
Menstrual disturbances in women — heavier, longer or irregular bleeding
Water retention — e.g. a swollen face, swollen eyelids
SubclinicalSubclinical — TSH elevated, fT4 still normal
TSH is elevated, but fT3 and fT4 are still within the normal range. Symptoms are often mild or absent entirely. Relatively common, especially in older women. Whether and when treatment is advisable is decided individually — taking into account the level of TSH, any symptoms and the antibody status.³˒⁴
OvertTSH elevated + fT4 reduced — levothyroxine usually clearly indicated
TSH is elevated and fT4 reduced. Symptoms are usually present, and levothyroxine is usually clearly indicated.
A single elevated TSH is not enough for the diagnosis
A follow-up check after a few weeks is usually recommended — the TSH value can be temporarily elevated, e.g. due to acute illness, stress or certain medications.
5. Diagnosis
TSH: The most important screening value — usually elevated in hypothyroidism.
fT3 and fT4: In overt hypothyroidism, fT4 is reduced; in the subclinical form still within the normal range.
TPO antibodies: Positive in the majority of Hashimoto's patients. Can be detectable years before overt hypothyroidism.³
Tg antibodies: Less often positive, but also indicative.
Ultrasound: In Hashimoto's, often shows hypoechoic, inhomogeneous tissue, sometimes a reduced-size thyroid. Nodules are also assessed.
Additionally: Cholesterol (LDL often elevated in hypothyroidism), blood count, vitamin D, vitamin B12, iron/ferritin — accompanying deficiencies are common in Hashimoto's. A celiac screening can be useful.
Treatment usually consists of replacing the missing thyroid hormone as a tablet — with levothyroxine (L-thyroxine). With permanent hypothyroidism, lifelong intake is usually necessary. Correct intake is crucial.³
How to take it correctly
In the morning on an empty stomach, some time before breakfast
With a glass of water
Always at the same time of day
Alternative: evening intake (a few hours after dinner) — after consulting your doctor
Missed dose: usually make it up as soon as you remember
Keep a gap from
Coffee — at the earliest some time after taking it
Milk and dairy products
Calcium, iron, magnesium — a few hours' gap
PPIs (e.g. omeprazole, pantoprazole) — a few hours' gap
The starting dose and the target dose are determined individually — depending, among other things, on age, body weight and concomitant conditions. In older patients or those with heart conditions, the dose is usually increased especially slowly. TSH checks are usually done a few weeks after each dose change; once stably adjusted, at longer intervals.³˒⁴
Levothyroxine — liquid form (drops)
For swallowing difficulties or certain concomitant medications, the liquid form can be advantageous. More: Generics vs. original.
T3 combination therapy
Some patients do not feel completely well on levothyroxine despite normal TSH values. A combination of T4 (levothyroxine) and T3 (liothyronine) can be considered in individual cases — the current guideline position does not make a general recommendation. This decision is usually made by experienced endocrinologists. Thyroid extracts (e.g. from pigs) are generally not recommended by experts.
7. Hashimoto's and psychological burden
For many people affected, Hashimoto's is more than just a lab value. Even with well-adjusted levels, some report a significant psychological burden:³
Depressive mood and listlessness — can be misdiagnosed as an independent depression; with depression, always have the thyroid checked too
Persistent exhaustion (fatigue), sometimes even with normal TSH
Anxiety and mood swings
Frustration when symptoms are not taken seriously despite normal lab values
Selenium in Hashimoto's
Selenium can be considered in consultation with your endocrinologist — there are indications that it can lower TPO antibodies and improve subjective well-being (moderate evidence). An overdose should be avoided. Natural sources: Brazil nuts in moderation, fish, eggs.
Do I feel unwell despite normal values? Bring it up!
It can be useful to additionally check fT3, iron/ferritin, vitamin D and vitamin B12 — accompanying deficiencies are common in Hashimoto's and can intensify symptoms.
8. Living with hypothyroidism
Levothyroxine timing: As a rule, always take it at the same time of day and under conditions that are as similar as possible. A fixed routine helps — e.g. with an alarm or a brite reminder.
Check-ups: TSH is checked at regular intervals. After a dose change, a few weeks are usually waited before measuring again.
Diet: A special Hashimoto's diet is usually not necessary. A balanced, selenium-rich diet is usually sensible. Excessive soy consumption can impair levothyroxine absorption. Seaweed and kelp should usually be avoided with Hashimoto's. A gluten-free diet is only recommended with proven celiac disease.³
Sport: Recommended and can improve mood, energy and weight. With a well-adjusted thyroid, there are usually no restrictions.
Travel: Take levothyroxine with you; refrigeration is usually not needed (stable at room temperature). With time differences, usually take it at the usual local time. More: Medications when travelling.
Myxedema coma — rare emergency in severe untreated hypothyroidism
Signs: unconsciousness, hypothermia. If suspected, call 112 immediately. Occurs almost exclusively in previously unrecognized hypothyroidism.³
How brite helps you with hypothyroidism
Levothyroxine in the morning on an empty stomach, in good time before breakfast — brite reminds you on time and helps you keep an eye on your TSH values and well-being.
Intake reminder — levothyroxine in the morning on an empty stomach, in good time before breakfast: brite reminds you on time. Set up a reminder
Interaction check — levothyroxine + calcium, PPIs, iron? Check the gap for free. Check now
Health history — document TSH values, weight, energy and symptoms over time. Track your history
Digital medication plan — all medications clearly organized for endocrinology and your GP. Go to medication plan
With Hashimoto's or after thyroid surgery, usually yes. With temporary forms (e.g. after thyroid inflammation), intake can sometimes be time-limited. Levothyroxine should not be stopped on your own.³
Levothyroxine is best absorbed on an empty stomach. Food, coffee and certain medications (e.g. calcium, iron, PPIs) can significantly reduce its absorption. An alternative is evening intake (a few hours after dinner) — after consulting your practice.
At the correct dose, levothyroxine usually does not cause weight gain — it only replaces the missing hormone. Weight gain is usually a symptom of the underactivity itself (slowed metabolism, water retention). On well-adjusted levothyroxine, weight often normalizes.
According to current knowledge, no. But the symptoms are usually fully treatable with levothyroxine. Selenium can be considered as an add-on in consultation with your endocrinologist. With well-adjusted levels, those affected can usually lead a completely normal life.³
Possible reasons: TSH is within the normal range, but possibly not in the range that is optimal for the individual. fT3 could be low. Accompanying deficiencies (iron/ferritin, vitamin D, vitamin B12) are common in Hashimoto's and can intensify symptoms. In these cases, seeing an endocrinologist can be sensible.
TSH is elevated, but fT4 is still within the normal range. Symptoms can be mild or absent. Whether treatment is advisable is decided individually — taking into account symptoms, antibody status and the level of TSH.³˒⁴
Selenium may be able to lower TPO antibodies and improve subjective well-being (moderate evidence). The dosage should be discussed with your endocrinologist; an overdose is to be avoided. Natural sources: Brazil nuts (in moderation), fish and eggs.
Only with proven celiac disease — Hashimoto's and celiac disease occur together more frequently (a screening can be useful). Without celiac disease, there is, according to current knowledge, insufficient evidence that a gluten-free diet improves Hashimoto's.
A rare, life-threatening emergency in severe, long-term untreated hypothyroidism. Signs include unconsciousness and hypothermia. If suspected, call the emergency number 112 immediately. Occurs almost exclusively in previously unrecognized hypothyroidism.³
Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or treatment. Levothyroxine should not be stopped or have its dose changed on your own. If a myxedema coma is suspected (unconsciousness, hypothermia), call the emergency number 112 immediately. The dosage is always determined individually by the treating doctor. Last updated: April 2026.
