Thyroid Disease Symptoms: Hypothyroidism and Hyperthyroidism
The thyroid gland weighs about 20–30 grams — less than a medium apple. Yet when it malfunctions, the effects are felt throughout the entire body: weight, mood, heart rate, skin condition. The problem is that thyroid symptoms are easy to dismiss as stress, fatigue, or ageing. This article explains how to recognise hypothyroidism and hyperthyroidism, which tests to order, and what to do if a nodule is found.
Hypothyroidism: when the thyroid is too slow
Hypothyroidism is a condition in which the thyroid produces fewer hormones than the body needs. Metabolism slows, and the body effectively enters an energy-saving mode. It affects about 2–3% of adults, and is roughly 5–8 times more common in women than in men.
Symptoms develop gradually, often imperceptibly:
- persistent fatigue and drowsiness that doesn't improve with sleep;
- feeling cold when others are comfortable;
- weight gain without changes in diet;
- constipation;
- dry skin, brittle nails, hair loss;
- slowed thinking and speech ("brain fog");
- puffiness of the face, hands, and legs;
- depression, apathy, loss of motivation;
- menstrual irregularities in women;
- slow heart rate (below 60 beats per minute).
An important caveat: hypothyroid symptoms are highly non-specific. Fatigue, weight gain, and dry skin occur in dozens of other conditions. This is why diagnosis must be confirmed by lab tests, not symptoms alone.
The most common cause is Hashimoto's thyroiditis — an autoimmune condition in which the immune system mistakenly attacks the thyroid. It is frequently diagnosed incidentally or years after symptoms begin.
Hyperthyroidism: when the thyroid is too fast
Hyperthyroidism is the opposite: the thyroid produces too many hormones. Metabolism accelerates, and the body runs at a constant high speed.
Characteristic symptoms of hyperthyroidism:
- rapid heartbeat (tachycardia), a feeling that the heart is pounding;
- weight loss despite a good or increased appetite;
- tremor in the hands;
- excessive sweating and heat intolerance;
- irritability, anxiety, nervousness;
- sleep disturbances;
- diarrhoea or frequent bowel movements;
- bulging eyes (exophthalmos) — characteristic of Graves' disease;
- enlargement of the thyroid gland (goitre).
The most common cause of hyperthyroidism is Graves' disease — an autoimmune condition in which the immune system stimulates the thyroid to overproduce hormones. Less commonly, the cause is a toxic nodular goitre or transient thyroiditis.
Thyroid tests: what to order and when
Key laboratory markers:
- TSH (thyroid-stimulating hormone) — the primary screening test. Normal range: 0.4–4.0 mIU/L. TSH is elevated in hypothyroidism and suppressed in hyperthyroidism. Order this first.
- Free T4 (free thyroxine) — normal range: 0.8–1.8 ng/dL (10–23 pmol/L). Low in hypothyroidism, high in hyperthyroidism.
- Free T3 (free triiodothyronine) — normal range: 2.3–4.2 pg/mL (3.5–6.5 pmol/L). Used in extended evaluation.
- Anti-TPO antibodies — marker of Hashimoto's thyroiditis. Normal: below 35 IU/mL (varies by lab). Elevated antibodies with normal TSH indicate an increased future risk of hypothyroidism.
- TSH receptor antibodies (TRAb) — characteristic of Graves' disease. Ordered when hyperthyroidism is suspected.
Tests can be taken at any time of day; fasting is not required. Exception: if you're already taking thyroid hormone replacement (levothyroxine), ask your doctor when to schedule the test.
Thyroid ultrasound is also useful — it evaluates the gland's size, structure, and the presence of nodules. It doesn't replace blood tests but adds important context.
Thyroid nodules: should you be concerned
Thyroid nodules are extremely common. Studies show they are detected on ultrasound in 19–68% of adults, depending on the population and imaging method. The vast majority are benign and require no treatment.
Key facts about nodules:
- Nodules under 1 cm — generally require only monitoring with a follow-up ultrasound every 1–2 years.
- Nodules over 1 cm or nodules with suspicious ultrasound features — fine-needle aspiration biopsy (FNA) is indicated to rule out malignancy.
- Malignant nodules account for about 5–10% of all those detected. When found early, thyroid cancer is highly treatable.
See a doctor promptly if you notice:
- rapid growth of a nodule;
- hoarseness without a cold;
- difficulty swallowing or breathing;
- enlargement of neck lymph nodes.
The thyroid and weight: a direct connection
One of the most common questions: "Could my thyroid be why I can't lose weight?" The answer: sometimes, but less often than people assume.
In hypothyroidism, the metabolism slows and the body retains water and accumulates fat. But the weight gain directly attributable to the hormonal imbalance rarely exceeds 3–5 kg — the rest is usually diet and activity. Treating hypothyroidism with levothyroxine normalises metabolism but is not a weight-loss medication.
If thyroid tests are normal and weight won't shift, the cause likely lies elsewhere: insulin resistance, sleep deprivation, chronic stress, or an unsuitable diet.
If you're concerned about thyroid-related symptoms, try describing them to the assistant — it will help you decide whether to see an endocrinologist or whether a GP is the right first step.
Frequently asked questions
Should I get a TSH test as a preventive measure?
Yes, especially for women over 35, people with a family history of thyroid disease, during pregnancy, and when symptoms are present. TSH screening is inexpensive and can catch problems before significant symptoms develop.
What is the difference between subclinical and overt hypothyroidism?
In subclinical hypothyroidism, TSH is elevated (typically 4–10 mIU/L) but free T4 remains normal. Symptoms may be mild or absent. The decision to treat depends on TSH level, symptoms, pregnancy status, and other factors — a doctor makes this call.
Can I take thyroid hormones without a prescription?
No. Self-medicating with thyroid hormones is dangerous. Even a small excess of levothyroxine causes rapid heartbeat, arrhythmias, bone density loss, and other serious consequences. Dosing is managed and monitored by a doctor.
Does diet affect the thyroid?
Yes. Iodine is essential for thyroid hormone synthesis — primary dietary sources include sea fish, shellfish, and iodised salt. Iodine deficiency is a common cause of goitre in certain regions. That said, excess iodine is also harmful, particularly in autoimmune thyroid disease. Don't take iodine supplements without medical advice.
What is Hashimoto's thyroiditis?
Hashimoto's thyroiditis is the most common cause of hypothyroidism. The immune system produces antibodies against thyroid tissue, gradually impairing its function. There is no specific treatment for the underlying autoimmune process — only its consequence, hypothyroidism, is treated with hormone replacement therapy.
Can hypothyroidism be cured permanently?
In most cases, hypothyroidism requires lifelong hormone replacement. This doesn't mean poor quality of life — with the correct dose, a person lives and feels completely normally. One exception is postpartum thyroiditis, which often resolves on its own within several months.
Symptomatica is an informational reference service. Not a medical service; does not diagnose or prescribe treatment. For any symptoms, please consult a doctor.