Goitre
How a shortage of thyroid hormone, most often from too little iodine, raises TSH and enlarges the thyroid, how a diffuse goitre becomes multinodular, why some nodules start making hormone on their own, and what a large goitre compresses.
By the end, you can
- Explain how TSH controls both the function and the growth of follicular cells, and why limited hormone synthesis enlarges the gland.
- Explain why most people with a simple or endemic goitre keep normal thyroid function.
- Describe the hyperplastic, colloid and multinodular stages of goitre, with their gross and microscopic appearance.
- Explain how activating mutations make nodules autonomous in toxic multinodular goitre and toxic adenoma, and predict the scan and blood tests.
- Relate the neck anatomy to the compressive effects of a large or retrosternal goitre, and explain how each treatment acts on the mechanism.
What it is
A goitre is any enlargement of the thyroid gland. It is diffuse or nodular, and non-toxic (normal function, the commonest), toxic (too much hormone) or hypothyroid. Most goitres arise from a sustained TSH drive when hormone synthesis is limited, above all by iodine deficiency (endemic goitre); others come from Graves disease, Hashimoto thyroiditis or tumours.
3 types to tell apart
- Simple diffuse goitre
- An even enlargement from TSH drive, in iodine deficiency or when demand rises (puberty, pregnancy); function usually normal.
- Non-toxic multinodular goitre
- Years of stimulation and involution with uneven, partly clonal growth leave many nodules; function normal.
- Toxic multinodular goitre and toxic adenoma
- One or more nodules make hormone autonomously, without TSH, so TSH is suppressed and the person is thyrotoxic.
US spelling: tumours → tumors.
Normal function
TSH sets both the output and the size of the thyroid
The lies in front of the below the : two lobes, such as the , joined by an . It sits inside the pretracheal fascia, attached to the larynx, so it rises on swallowing; a goitre moves the same way, which helps tell it from other lumps in the neck.
Its follicles need iodine, from food and water, to make thyroxine (T4) and triiodothyronine (T3): each T4 carries four iodine atoms and each T3 three. Follicular cells trap iodide actively and keep a store of hormone in their colloid.
Thyroid-stimulating hormone (TSH) from the pituitary is a growth signal as well as a signal to secrete: acting through the TSH receptor and cyclic AMP, it makes follicular cells taller (hypertrophy) and more numerous (hyperplasia). Feedback keeps TSH just high enough to meet the body’s need for hormone, so the gland normally stays the same size.
Underlying change · Step 1 of 4
Too little hormone made: TSH drives the gland to grow
The full lesson is part of Student Pro
It takes you through all 4 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 4
Hyperplasia, colloid involution and nodules
The full lesson is part of Student Pro
It takes you through all 4 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 4
Nodules that escape TSH: toxic multinodular goitre and toxic adenoma
The full lesson is part of Student Pro
It takes you through all 4 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 4 of 4
A large goitre presses on the neck
The full lesson is part of Student Pro
It takes you through all 4 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 4 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 4 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 4 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 4 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 4 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 .