Hyperthyroidism

Question 1

How common is it?

Answer 1

• Prevalence = 400 per 100,000 persons. Lifetime risk of 1% in men and up to 2% in women.

Question 2

What causes it?

Answer 2

Grave’s disease
- 0.5% prevalence (2/3 cases hyperT).

Autoimmune cause (IgG).

• Triggers = stress, infection, childbirth.
• Associated with other AI conditions: vitiligo, type 1 DM, Addison’s.

Toxic Multinodular Goitre
- In elderly and iodine-deficient areas. There are nodules that secrete thyroid hormones.

Toxic adenoma
- Solitary nodule producing T3 and T4.

Ectopic thyroid tissue
- Metastatic follicular thyroid cancer, or struma ovarii: ovarian teratoma with thyroid tissue.

Exogenous
- Iodine excess, eg food contamination, contrast media. Levothyroxine excess.

Others

• Subacute de Quervain’s thyroiditis (post-viral, painful goitre).
• Drugs – amiodarone, lithium.
• Postpartum
• TB (rare)

Question 3

Risk factors?

Answer 3

Family history, more common in women than men.

Question 4

How does it present?

Answer 4

Symptoms
- Diarrhoea, weight loss, increased appetite, over active, sweats, heat intolerance, palpitations, tremor, irritability, liable emotions, oligomenorrhoea ± infertility. Rarely psychosis, chorea, itch, panic, alopecia, urticarial.

Signs
- Pulse fast/irregular, warm moist skin, fine tremor, palmar erythema, thin hair, lid lag, lid retraction (exposure of sclera above iris). May be goitre, nodules or bruit depending on cause.

Signs of Grave’s disease
1. Eye disease – exophthalmos, opthalmoplegia.
2. Pretibial myxoedema – odematous swellings above lateral malleoli.
3. Thyroid acropachy – extreme manifestation, with clubbing, painful finger and toe swelling and periosteal reaction in limb bones.
Complications
- Heart failure (thyrotoxic cardiomyopathy), angina, AF, osteoporosis, opthalmopathy, gynaecomastia.

Question 5

Differential diagnoses?

Answer 5

Thyrotoxicosis, Grave’s disease, euthyroid hyperthyroxinaemia, Struma ovarii.

Question 6

Investigations?

Answer 6

• TSH↓ (suppressed), T3 and T4↑.
• May be mild normocytic anaemia, mild neutropenia (Grave’s), ESR↑, Ca2+↑, LFT↑.
• Check thyroid antibodies.
• Test visual fields, acuity and eye movements.

Question 7

Treatments?

Answer 7

1. Drugs – β-blockers for rapid symptom control. Anti-thyroid medication – carbimazole. Give thyroxine and carbimazole together – reduces risk of iatrogenic hypoT.
2. Radioiodine – Most become hypoT post-treatment. Contraindicated in pregnancy and lactation.
3. Thyroidectomy – Carries risk of damage to recurrent laryngeal nerve and hypoparathyroidism. Patients may become hypothyroid.