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Thyrotoxicosis

Title

Ñ    Thyrotoxicosis

Definition

Ñ    Metabolic state caused by excess thyroxine

Pathogenesis

Causes

Primary Thyroid Disease

Ñ    Grave’s disease:

IgG antibody binds to TSH receptor and stimulates production of thyroxine

Ñ    Toxic multinodular goitre

Ñ    Toxic solitary adenoma

Ñ    Thyroiditis:

Sub-acute, viral, de Quervain’s

Silent, painless

Post partum

Extra-Thyroid Diseases

E&M

Ñ    TSH secreting pituitary adenoma

Ñ    Metastatic thyroid carcinoma:

Follicular

RAG

Ñ    Hydatidiform mole, choriocarcinoma

Ñ    Struma ovarii:

Teratoma that contains thyroid tissue

Ñ    Gestational thyrotoxicosis

Drugs

Ñ    Amiodarone

Ñ    Thyrotoxicosis factitia:

Surreptitious ingestion of thyroxine tablets

Pathophysiology

Ñ    Increased production of thyroxine results in increased physiological effects of thyroxine

Clinical Features

History

Sex

Ñ    Females > Males

E&M

Ñ    Weight loss

Ñ    Heat intolerance

IS

Ñ    Increased sweating

CVS

Ñ    Palpitations

GIT

Ñ    Increased appetite

Ñ    Diarrhoea

RAG

Ñ    Menstrual disturbances in females:

Especially oligomenorrhoea

Ñ    Subfertility

CNS

Ñ    Restlessness

Ñ    Irritability

RS

Ñ    Dyspnoea:

Retrosternal goitre

Examination

E&M

Ñ    Loss of weight

Ñ    Goitre

IS

Ñ    Increased sweating

Ñ    Pretibial myxoedema

Ñ    Clubbing

Ñ    Onycholysis

Ñ    Palmar erythema

CVS

Ñ    Tachycardia

Ñ    Atrial fibrillation

Ñ    Cardiac failure

RAG

Ñ    Gynaecomastia

CNS

Ñ    Chemosis

Ñ    Lid retraction

Ñ    Lid lag

Ñ    Exophthalmos

Ñ    Proptosis

Ñ    Ocular palsies

Ñ    Papilloedema

Ñ    Tremor

Ñ    Choreoathetosis

Ñ    Proximal myopathy

RS

Ñ    Stridor:

Retrosternal goitre

Ñ    Pemberton’s sign:

Retrosternal goitre

Complications

Thyroid crisis (thyroid storm)

Ñ    Precipitating factors:

Stress, infection, surgery in an unprepared patient, radioiodine therapy

Ñ    Effects:

Hyperpyrexia, severe tachycardia, severe restlessness

Investigations

Fluids

Blood

Biochemistry

Ñ    TSH levels:

·          Suppressed

·          Rarely increased:

Pituitary disease

Ñ    T₄, T ₃ levels:

Raised

Immunology

Ñ    Thyroid stimulating antibodies:

Grave’s disease

Management

Symptomatic Relief

Drugs

Ñ    Beta-adrenergic blockers

Control

Drugs

Ñ    Thiourea compounds:

Carbimazole, methimazole, propylthiouracil

Regimes used

Ñ    Titration regime:

Carbimazole, beta-blocker 4-6weeks

When clinically and biochemically euthyroid stop beta blocker

After 2-3 months, if controlled, gradually reduce carbimazole over 6-24 months

When euthyroid on 5 mg daily, stop carbimazole

Ñ    Block and replace regime:

Full dose of carbimazole to suppress thyroid activity

Replace with thyroxine 100 micrograms daily

Continue for 18 months (usually)

Surgery

Ñ    Thyroidectomy

Radiotherapy

Ñ    Radioactive iodine:

Toxic multinodular goitre

Grave’s disease

Toxic adenoma

Thyroid Crisis

Ñ    Propranolol

Ñ    Potassium iodide

Ñ    Antithyroid drugs

Ñ    Steroids

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