Thyroid terms, plain English.

Goitre

An enlargement of the thyroid gland, visible or felt as a swelling in the front of the neck.

Graves' disease

An autoimmune condition in which the immune system over-stimulates the thyroid, causing hyperthyroidism.

Hashimoto's thyroiditis

An autoimmune condition in which the immune system gradually damages the thyroid, often leading to hypothyroidism.

Hyperthyroidism

A condition in which the thyroid produces too much hormone, speeding up many body processes.

Hypothyroidism

A condition in which the thyroid does not produce enough hormone, slowing many body processes.

Subclinical hypothyroidism

A mild form where TSH is above the reference range but free T4 is still normal, often without obvious symptoms.

Thyroid eye disease

An autoimmune condition affecting the tissues around the eyes, most commonly associated with Graves' disease.

Thyroid nodule

A lump or growth within the thyroid gland - the vast majority are benign, but all should be assessed.

Thyroid storm

A rare, life-threatening emergency caused by extreme hyperthyroidism - requires immediate hospital treatment.

FNA biopsy

Fine needle aspiration - a quick outpatient procedure to sample cells from a thyroid nodule for examination.

Free T3 (free triiodothyronine)

The most potent, unbound thyroid hormone - active in cells; sometimes tested when T4 results are unclear.

Free T4 (free thyroxine)

The active, unbound form of the thyroid's main hormone - a key marker of thyroid output.

TgAb (thyroglobulin antibodies)

Antibodies that target thyroglobulin - measured alongside Tg in thyroid-cancer follow-up because they can interfere with the result.

Thyroglobulin

A protein made only by thyroid cells - used mainly as a surveillance marker after thyroid cancer treatment.

Thyroid antibodies

Proteins produced by the immune system that target thyroid tissue - a marker of autoimmune thyroid disease.

Thyroid ultrasound

A painless imaging test using sound waves to visualise the thyroid gland and any nodules within it.

TPO antibodies

Antibodies targeting thyroid peroxidase - the main marker of Hashimoto's thyroiditis, also raised in Graves' disease.

TRAb (TSH receptor antibodies)

Antibodies that bind to and stimulate the TSH receptor on the thyroid - the hallmark of Graves' disease.

TSH (thyroid-stimulating hormone)

The pituitary's messenger hormone that tells the thyroid how much hormone to produce - the cornerstone thyroid blood test.

Carbimazole

An antithyroid drug that reduces thyroid hormone production - the main medical treatment for hyperthyroidism in the UK.

Levothyroxine

A synthetic form of T4 used to treat hypothyroidism - taken once daily, usually on an empty stomach.

Liothyronine (T3)

A synthetic form of the active thyroid hormone T3 - occasionally used alongside or instead of levothyroxine.

Propylthiouracil (PTU)

An antithyroid drug used mainly in the first trimester of pregnancy or when carbimazole is not suitable.

Radioactive iodine (RAI)

A treatment using radioactive iodine to reduce or destroy overactive or cancerous thyroid tissue, given as a capsule or drink.

Hemithyroidectomy

Removal of one lobe of the thyroid - the remaining lobe may keep thyroid function intact.

Isthmusectomy

Removal of just the isthmus - the narrow strip of thyroid tissue connecting the two lobes.

Thyroidectomy

Surgery to remove all or part of the thyroid gland.

Total thyroidectomy

Removal of the entire thyroid gland - results in permanent hypothyroidism requiring lifelong levothyroxine.

Isthmus

The narrow band of thyroid tissue connecting the two lobes across the front of the windpipe.

Thyroid gland

A butterfly-shaped gland in the neck that produces hormones controlling metabolism.

Thyroid lobe

One of the two halves of the thyroid gland, sitting either side of the windpipe.

Brain fog

The foggy, slowed-down thinking - poor memory, concentration and word-finding - that many people get with thyroid problems.

Endocrinologist

A hospital doctor who specialises in hormonal conditions, including thyroid disorders.

Euthyroid

A term meaning the thyroid is functioning normally - producing the right amount of hormone.