Hyperthyroidism

Hyperthyroidism

Causes
1. Grave's disease: F:M: 9:1, 30-50yo, autoimmune dis caused by stimulatory TSH-receptor antibodies. Diffuse thyroid enlargement, usually become hyperthyroid but may be hypo/euthyroid. Assoc with other autoimmune diseases.
2. Toxic multinodular goitre: in elderly and iodine def areas. Nodules that secrete thyroid hormone.
3. Toxic adenoma: solitary nodule producing T3 and T4. On isotope scan the nodule is 'hot' and the rest of the gland suppressed.
4. Others: Subacute(de Quervain's) thyroiditis: a self-limiting viral infection with painful goitre, fever and raised ESR. Drugs: Amiodarone, lithium (tho hypothyroidism is commoner). Exogenous iodine: thyroxine intoxication - raised t4, reduced T3 and thyroglobulin. Occ seen with iodine excess ie contrast media, food contamination. Ectopic thyroid tissue: metastatic follicular thyroid cancer, choriocarcinoma or struma ovarii (ovarian teratoma containing thyroid tissue).
Features
1. Symptoms: weight loss, increased appetite, (paradoxical weight gain in 10-30%), heat intolerance, sweating, diarrhoea, tremor, irritability, frenetic activity, emotional lability, psychosis, itch, oligomenorrhoea-may cause infertility.
2. Signs: raised HR, AF, warm peripheries, fine tremor, palmar erythema, hair thinning, lid lag, lid retraction, may be goitre, thyroid nodules or bruit depending on cause.
3. Features specific for Graves': exophthalmos, opthalmoplegia. Pretibial myxoedema: oedematous swellings above lateral malleoli, thyroid acropatchy: clubbing, painful finger and toe swelling, periosteal reaction in limb bones.
4. Complications: heart failure (esp in elderly), angina, AF, osteoporosis, opthalmopathy, gynaecomastia, thyroid storm.
5. Features of thyrotoxic storm: fever, agitation, confusion, coma, tachycardia, AF, D&V, goitre, thyroid bruit, 'acute abdomen'. Precipitents: recent thyroid surgery or radioiodine, infection, MI, trauma.
Investigations
1. Key: Thyroid function tests: suppressed TSH, raised T3 & T4, FBC: mild normocytic anaemia and mild leucopenia, raised ESR, raised calcium, raised LFTs.
2. Also: check thyroid autoantibodies, isotope scan if cause is unclear to detect nodular disease or subacute thyroiditis. If opthalmopathy test visual fields, acuity and eye movements. In thyrotoxic storm technetium uptake is diagnostic but do not delay treatment for this.
Management
1. Pharma: B-blockers ie propanolol for symptom control, Anti-thyroid medication: either titration with carbimazole, gradually reducing dose. Or block and replace with simultaneous carbimazole and thyroxine (less risk of hypothyroidism). In Graves' maintain on therapy for 12-18 months then withdraw, ~50% will relapse= radioiodine or surgery.
  1. Carbimazole SEs: agranulocytosis = sepsis - rare but can be life-threatening. Warn to stop and get urgent FBC if signs of infection. Alternative drug: propylthiouracil.
2. Radioiodine: most become hypothyroid. No evidence of increased cancer, birth defects or infertility. CI: pregnancy and lactation. Caution in active hyperthyroidism as risk of thyroid storm.
3. Surgery: thyroidectomy. Risk of damaging RLN: horseness and hypoparathyroidism. Pts may become hypo or hyperthyroid.
4. Seek expert help in pregancy/infancy.
5. Thyrotoxic storm: Get expert help, give IV saline, NG tube if vomiting, take blood for T3, T4, cultures (if suspect infection), sedate if necessary with chlorpromazine, if no contraindication give propanalol, high-dose digoxin, Anti-thyroid drugs: carbimazole and after 4hrs Lugol's solution.. IV hydrocortisone or PO dexamethasone. Tx suspected infection with cefuroxime. Cool with tepid sponging/paracetamol. After 5d reduce carbimazole, after 7d stop Lugol's solution, after 10d stop propanolol and iodine.

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