Thyroiditis
How autoimmunity, viruses, bacteria and fibrosis injure the thyroid follicles, why fast destruction leaks stored hormone (thyrotoxicosis with a low iodine uptake, then hypothyroidism), and how each form looks.
By the end, you can
- Explain why the thyroid’s store of hormone lets destruction cause thyrotoxicosis without any increase in production.
- Contrast the mechanism and microscopy of Hashimoto, painless and postpartum, subacute granulomatous, acute suppurative and Riedel thyroiditis.
- Explain why radioactive iodine uptake is low in destructive thyroiditis and why a hypothyroid phase usually follows.
- Relate chronic thyroiditis to fibrosis, atrophy, compression of the neck and the risk of thyroid lymphoma.
- Recognise the tests, classic appearances and numbers examiners ask for, and explain how each treatment acts on the mechanism.
What it is
Thyroiditis is inflammation of the thyroid gland. Its forms divide by cause and pace: autoimmune (chronic Hashimoto thyroiditis, and transient painless and postpartum thyroiditis), subacute granulomatous (de Quervain, after a viral illness), acute suppurative (bacterial), drug- or radiation-induced, and Riedel (fibrosing). Fast destruction releases stored hormone (destructive thyroiditis); slow destruction leads to hypothyroidism.
5 types to tell apart
- Hashimoto thyroiditis
- Chronic autoimmune destruction with lymphoid follicles and Hürthle cells; the commonest cause of hypothyroidism where iodine intake is adequate.
- Painless (silent) and postpartum thyroiditis
- A milder, transient autoimmune thyroiditis; postpartum thyroiditis follows childbirth. Thyrotoxic, then hypothyroid, then usually normal.
- Subacute granulomatous (de Quervain) thyroiditis
- A painful, tender gland weeks after a viral illness, with giant cells round escaped colloid; the same three-phase course.
- Acute suppurative thyroiditis
- A rare bacterial infection with pus or an abscess, often through a congenital fistula from the throat in children.
- Riedel thyroiditis
- Rare, dense fibrosis that replaces the gland and grows through its capsule into the neck; often part of IgG4-related disease.
Normal function
Follicles keep weeks of hormone in store
The thyroid is built of follicles: hollow spheres of round a store of , a gel of the protein thyroglobulin. The cells trap iodide from the blood in the , and the enzyme thyroid peroxidase attaches it to thyroglobulin, building thyroxine (T4) and a little triiodothyronine (T3) that stay bound in the colloid.
Release is a separate step controlled by thyroid-stimulating hormone (TSH): the cells take colloid back in, cut the hormone free and pass it to the blood. The hold weeks of hormone, so release and new production can come apart. That is the key to thyroiditis: if follicle walls break, the store escapes at once, whatever TSH is doing.
Trapping iodide needs healthy follicular cells driven by TSH. A small tracer dose of radioactive iodine therefore measures how hard the gland is making hormone, not how much hormone is in the blood. In a healthy gland only scattered lymphocytes lie in the tissue between the follicles.
Underlying change · Step 1 of 5
Autoimmune attack: Hashimoto, painless and postpartum thyroiditis
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
After a virus or from bacteria: subacute and acute thyroiditis
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
Broken follicles leak their store: thyrotoxicosis with low uptake
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
Thyrotoxic, then hypothyroid, then usually normal again
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Fibrosis, atrophy and spread into the neck
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .