Hyperthyroidism

Question 1

How common is it?

Answer 1

0.75% prevelance

Question 2

Who does it affect?

Answer 2

10 times more common in women than men. The prevalence of subclinical hyperthyroidism increases with age and is higher in iodine-deficient areas such as Denmark.

Question 3

What causes it?

Answer 3

Graves’ disease is by far the most common cause: Thyroid stimulating antibodies (IgG) bind to TSH receptors and stimulate the thyroid. Thyroid gland hypertrophies and becomes diffusely enlarged.

TSH secreting pituitary adenoma.

T3 T4 secreting site in the thyroid (nodule in a multinodular goitre, adenoma or (v rarely) carcinoma.

Thyroiditis: Large amounts of preformed hormones are released after the destruction of follicles, with transient thyroid toxicosis.

Exogenous intake of thyroid hormones (factitious thyrotoxicosis).

Question 4

What risk factors are there?

Answer 4

Female
FHx
smoking
low iodine intake
autoimmune 
diseases (such as type 1 diabetes)

Question 5

How does it present?

Answer 5

Weight loss
heat intolerance
sweating (due to stimulated metabolism). 
Tremor
nervousness
irritability
emotional disturbance
tiredness and lethargy
palpitations
tachycardia
arrhythmias
Eye signs

Question 6

What is a thyroid storm?

Answer 6

Rare presentation of extreme signs of thyrotoxicosis and severe metabolic disturbances.

Precipitated by non-thyroid surgery, major trauma, infection, imaging studies with iodinated contrast medium in patients with unrecognised thyrotoxicosis.

Features are: Insomnia, anorexia, vomiting, diarrhoea, marked sweating, fever, marked tachycardia.

Question 7

Investigations

Answer 7

TFTs. Decreased FSH level and increased T4 and free T3 (in all cases apart from pituitary).
+ve serology for thyroid autoantibodies.
Radioactive iodine scan (or technetium scan)

Question 8

Treatment

Answer 8

Medical: Antithyroid drugs block hormone synthesis: Carbimazole 20mgbd. β-blockers are used to control tachycardia and tremor. Radioactive iodine. Contraindicated in severe eye disease, young women, patients who are the main carers of small children

Surgical: Total thyroidectomy (for graves). Indicated in patients who are not candidates for I131 therapy. Treatment of choice for those with the eye condition or whom medication is not effective. Risk of RLN injury and hypoparathyroidism (due to increased vascularity of the gland and the local fibrosis). Thyroid lobectomy: for isolated nodules or adenomas.

Question 9

Conditions that would present similarly

Answer 9

AF (for palpitations + tachycardia). Panic attacks. Also has some of the same symptoms as parkinsons.