Hyperthyroidism

http://www.eurekalert.org/pub_releases/2016-08/mali-ngf081716.php

Hyperthyroidism/thyrotoxicosis:
Common clinical syndrome characterised by hypermetabolism and increased serum levels of free thyroid hormone. F5x>M. Prevalence of about 20/1000 in females.

Aetiology:
Due to increased release of thyroid hormones (T4 and T3) – Graves disease (diffuse toxic goitre); TSH induced (eg inappropriate secretion by pituitary); tumours; thyroiditis; iodine ingestion (eg drugs, radiographic contrast media).

Clinical features:
Usually develops insidiously – often symptoms for up to 6 months before presentation. Most body systems are affected and there is a great individual variation in clinical features.
Commonly – goitre, tachycardia, skin is warm and moist, fine tremor, atrial fibrillation, hypersensitivity to heat/heat intolerance, fatigue, weight loss with normal or increased appetite, insomnia, hair thins, pruritis, onycholysis, frequent stools. Painless proximal muscle weakness occurs in up to 70%. Hyperreflexia. Osteoporosis.
Eyes – stare, lid lag, lid retraction. In Graves  infiltrative ophthalmopathy
Thyroid acropachy – rare complication of Graves disease  hands swell, clubbing of digits and periostitis.

Diagnosis – clinical features and laboratory studies.

Graves disease – most common cause of hyperthyroidism – autoimmune disease – antibody to TSH receptor on thyroid is produced; associated with HLA-B8, DR3 and DR2. Usually females aged 30-50. Distinguished from other forms due to diffuse thyroid enlargement (2-3x larger). Ophthalmological involvement is common. Associated with diabetes mellitus and pernicious anaemia.

Thyrotoxic crisis (thyroid storm) – when hormone levels become extremely high  hyperthermia, fever, vomiting, weakness, tachycardia  coma (life threatening). Usually precipitated by acute illness (eg stroke, infection, surgery, diabetic ketoacidosis) in those with a partially or untreated hyperthyroidism.

Treatment:
Antithyroid drugs (carbimazole, methimazole) – reduce synthesis of thyroid hormone by inhibition the iodination of tyrosine. Carbimazole is also immunosuppressive); radioactive sodium iodine (destroys function of thyroid cells); surgical thyroidectomy (especially if <40yrs, poor response to drugs or if severe)

Involvement of feet:
Hyperhidrosis
Ankle oedema
Onycholysis
Osteoporosis.
Peripheral neuropathy (rare)  mostly absent reflexes – Basedow’s paraplegia.
Pretibial myxoedema – can affect dorsal hallux

 
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