The thyroid is a small gland situated at the base of the neck. It produces the hormones that regulate the body’s metabolic rate. When it is underactive, there are numerous but non-specific signs: tiredness, feeling the cold, weight gain, constipation and brittle hair. In women, certain thyroid-related symptoms may go unnoticed or be mistaken for other conditions. They are therefore easily attributed to stress, the start of the new school term or the menopause. In this article, Arnaud, a qualified pharmacist, explains which symptoms should raise a red flag. He then details the blood tests to ask for, how to interpret the results, and what natural remedies can — or cannot — offer.
What does the thyroid do, and what happens when it slows down?
The thyroid is situated at the base of the neck, in front of the windpipe. It functions like a thermostat. In practice, it absorbs iodine from the diet and uses it to produce two hormones: T4 and T3. These circulate throughout the body. They determine the rate at which each cell consumes energy.
The pituitary gland, a gland in the brain, controls this production. It secretes TSH, the hormone that regulates the thyroid. The system operates in a feedback loop: if the thyroid does not produce enough, the pituitary gland increases TSH levels to stimulate it. This is why measuring TSH levels is so useful. A high TSH level indicates that the pituitary gland is overstimulating the thyroid, meaning the thyroid is struggling to keep up.
Hypothyroidism is diagnosed when thyroid hormone production becomes insufficient. The slowdown occurs gradually, over several months. It therefore often goes unnoticed: people get used to feeling tired before they start to worry about it.
What thyroid symptoms should women be alert to?
The French National Health Insurance describes a wide variety of signs. This diversity also explains why it is so difficult to detect:
- Physical and mental fatigue: drowsiness, difficulty concentrating, and a less reliable memory. Above all, it is a form of fatigue that sleep does not alleviate.
- Sensitivity to the cold: feeling cold when those around you do not. This is the most commonly overlooked sign, and one of the most telling.
- Sluggish bowel movements: newly developed constipation, without any change in diet.
- Moderate weight gain, sometimes despite a reduced appetite.
- Skin, hair and nails: dry, brittle hair; fragile nails; pale, dry skin.
- Menstrual disorders: irregular periods, muscle cramps.
- Slowed heart rate, swollen eyelids, and a hoarser voice in established cases.
In practice, the most useful indicator is not the number of symptoms, but their duration. Post-holiday fatigue usually improves within two to three weeks, with a full night’s sleep and a regular routine. However, fatigue that persists warrants medical advice, especially if accompanied by two or three other symptoms.
In the pharmacy, we often see women attributing these symptoms to something else for months on end. They think it might be mental strain, returning to work, or perimenopause. The symptoms do, in fact, overlap considerably. The diagnosis therefore often only comes after a blood test carried out for another reason.
How can you tell if it’s a thyroid problem: which blood test should you ask for?
According to the National Health Service, the doctor will first prescribe a TSH test. If the result is abnormal, the laboratory will then measure free T4 (FT4). The good news is that the same blood sample is used, so there’s no need for another needle prick. It is the combination of these two values that helps determine the diagnosis.
The French National Authority for Health (HAS) makes an important clarification. It does not recommend routine screening for people without symptoms. In other words, it is the symptoms that justify the test. Hence the importance of knowing how to recognise them before seeing a doctor.
| TSH | Free T4 | Interpretation | Standard management |
|---|---|---|---|
| Normal | Not measured | Normal thyroid function | Look for another cause of the symptoms |
| Elevated ( > 4 mIU/L) | Low | Confirmed hypothyroidism | Treatment to be discussed with the doctor |
| Elevated (between 4 and 10 mIU/L) | Normal | Subclinical hypothyroidism | Follow-up at a later date before any decision is made |
| Very high (> 10 mIU/L, confirmed) | Normal or low | Situation to be reviewed | Treatment to be considered based on symptoms and cardiac risk |
The HAS also emphasises a principle that makes a significant difference. Treatment should not be decided on the basis of a single figure. The doctor and the patient must discuss this first. Indeed, the TSH level considered normal varies from person to person. A patient may therefore feel unwell even though her TSH remains within the reference range. If your symptoms persist despite test results being deemed normal, tell your doctor.
Why are thyroid problems and the menopause so often confused after the age of 40?
Both conditions often occur at the same age. Furthermore, they overlap to such an extent that one can mask the other. Take a 45-year-old woman, for example. She is putting on weight, has trouble sleeping, is losing her hair and is experiencing irregular periods. There are two possible explanations, each as plausible as the other. Yet there is nothing to help distinguish between them at first glance.
The key point can be summed up in a single sentence: attributing these symptoms to perimenopause remains a hypothesis, not a diagnosis. Until TSH levels have been measured, the possibility of a thyroid issue remains open.
Certain symptoms, however, point in one direction. Sensitivity to the cold and recent constipation suggest a thyroid issue. Conversely, hot flushes point towards perimenopause.
What can natural remedies offer for the thyroid?
The standard treatment for confirmed hypothyroidism is levothyroxine. This is a synthetic thyroid hormone. The doctor prescribes it and adjusts the dose based on blood tests. Natural approaches are therefore by no means a substitute for this.
That said, two micronutrients play a documented role.Iodine forms the basis of thyroid hormones: without it, the gland cannot produce them. Selenium, for its part, is involved in the conversion of T4 into T3, the active form. Europe recognises these two claims.
Caution is nevertheless advised, and this is the key message of this section. Never take iodine on its own if you have a known or suspected thyroid condition. An excess of iodine can indeed upset the balance of autoimmune thyroiditis or exacerbate hyperthyroidism. In practice, most people get sufficient iodine from their diet: fish, seafood, dairy products and iodised salt.
To find out more about herbal medicine and homeopathy for the thyroid, see our article ‘The Thyroid and Naturopathy: Natural Treatments’.
Our pharmacist Arnaud particularly recommends selenium supplements in oligotherapy. They provide a measured maintenance dose. They are therefore not intended to correct a deficiency, which requires a blood test and medical advice.
To view the full range, see our selection of oligotherapy products in our online pharmacy, chosen by our pharmacists.
What lifestyle changes should you make whilst waiting for test results?
This advice is not intended to treat a thyroid condition; it is simply to help narrow down the possible causes. If your fatigue subsides with these measures, it was probably not caused by a thyroid problem. If, on the other hand, it persists, there is a much stronger case for seeking medical advice.
- Regulate your sleep: go to bed and get up at the same time, including at weekends, for two to three weeks.
- Get some morning light: spend ten minutes outdoors within an hour of waking up. This helps reset your body clock.
- Stabilise blood sugar levels: have a protein-rich breakfast. This helps prevent that mid-morning slump, which is often mistaken for chronic fatigue.
- Keep a record of your symptoms: maintain a dated list of the symptoms you experience. This record will ensure your consultation is effective.
If fatigue is the main symptom, our selection of supplements for energy, vitality and fatigue can complement these measures. They should never replace a blood test if the symptoms persist.
A practical reminder is in order if you are already taking levothyroxine. This medicine should be taken in the morning, on an empty stomach, with a glass of water. The package leaflet advises leaving a gap of more than two hours between taking it and iron or calcium supplements, gastric protectants, resins and adsorbents. Vegetable charcoal is one such substance. Many unexplained imbalances are in fact caused by a supplement taken at the same time as the tablet.
When should you consult a doctor or your pharmacist?
In certain situations, you should not wait. This applies to swelling at the base of the neck, difficulty swallowing, a noticeably slow heart rate, or fatigue that interferes with daily life. Furthermore, if you are currently pregnant or planning a pregnancy, particular care is required. Thyroid function does, in fact, influence foetal development.
Important precautions:
- Never stop or change your levothyroxine treatment on your own, even if your symptoms improve.
- Do not take iodine without medical advice if you have a known or suspected thyroid condition.
- Tell your pharmacist about any supplements you are taking at the same time. Iron, calcium, magnesium and adsorbents can affect the absorption of the medicine.
- A normal test result does not mean you should not discuss persistent symptoms. The HAS emphasises that decisions should be made through consultation, not based on a single figure.
Sources
This article is based on the following recommendations and reference documents, consulted in August 2026:
- French National Health Insurance (ameli.fr) — Circumstances of detection, diagnosis and progression of hypothyroidism: list of symptoms, initial measurement of TSH followed by free T4.
- Haute Autorité de Santé — Hypothyroidism: patient-reported symptoms, clinical presentation and TSH levels are essential: screening not recommended for asymptomatic individuals, TSH cut-off levels, the role of doctor-patient dialogue in the decision to treat.
- ANSM — Patient information leaflet for a levothyroxine-based treatment (100 micrograms): to be taken in the morning on an empty stomach; must be taken at least two hours apart from iron or calcium salts, gastric protectants, resins and adsorbents.
- European Commission — Register of Nutrition and Health Claims: authorised claims for iodine and selenium regarding normal thyroid function.
This article is for information purposes only. It is not a substitute for medical advice. If you have persistent symptoms or are currently undergoing treatment, seek advice from your doctor or pharmacist.
Frequently asked questions about thyroid testing
Do I need to fast before a TSH test?
No, you do not need to fast for a TSH test. If you are already taking levothyroxine, have the blood test before taking your morning tablet. Ensure you maintain the same conditions between tests so that the results remain comparable.
Is a normal TSH level enough to rule out a thyroid problem?
In the vast majority of cases, yes: a normal TSH level makes hypothyroidism unlikely. However, the HAS points out that the normal range varies from person to person. A patient may therefore still experience symptoms even if their TSH level falls within the reference range. If symptoms persist, tell your doctor.
What is subclinical hypothyroidism?
Subclinical hypothyroidism is when the TSH level rises whilst free T4 remains within the normal range. This condition does not always require treatment. The HAS recommends first re-checking the TSH and T4 levels after a period of time. If levels exceed 10 mIU/L on two separate tests, treatment should be discussed with the patient.
Does a thyroid condition really cause weight gain?
Hypothyroidism can be accompanied by weight gain, which is usually moderate. The metabolism slows down and the body retains water. However, it does not, on its own, account for significant weight gain. Moreover, treatment does not cause weight loss: it simply restores normal function.
When should you consult a doctor or pharmacist if you have concerns about your thyroid?
Seek advice as soon as you experience fatigue lasting more than three weeks despite getting enough sleep. Seek advice even sooner if this is accompanied by feeling cold, recent constipation, hair loss or unexplained weight gain. Do not delay if you experience swelling in the neck, difficulty swallowing or a noticeably slow heart rate. Before seeing a doctor, your pharmacist can assess your symptoms and check your current treatments.
A dietary supplement is not a substitute for a varied and balanced diet or a healthy lifestyle.
