THYROID GLAND LEC 2

Hyperthyroidism
The term thyrotoxicosis is retained because hyperthyroidism, i.e. symptoms due to a raised level of circulating thyroid hormones, is not responsible for all manifestations of the disease.
Clinical types are:
• diffuse toxic goitre (Graves’ disease)
•toxic nodular goitre;
•toxic nodule;
•hyperthyroidism due to rarer causes.

Thyrotoxicosis is eight times more common in women than in men.
Clinical features
The symptoms are:
• tiredness;
• emotional lability;
•heat intolerance;
• weight loss;
• excessive appetite;
•palpitations.
The signs of thyrotoxicosis are:
• tachycardia;
• hot, moist palms;
• exophthalmos;
•lid lag/retraction;
•agitation;
•thyroid goitre and bruit.
The most significant symptoms are loss of weight despite a good appetite, a recent preference for cold, and palpitations.
The most significant signs are the excitability of the patient, the presence of a goitre, exophthalmos and tachycardia or cardiac arrhythmia.

Diffuse toxic goitre (Graves’ disease):
A diffuse vascular goitre, a thrill and a bruit may be present. It usually occurs in younger women and is frequently associated with eye signs. 50% of patients have a family history of autoimmune endocrine diseases.
The thyroid tissue is hypertrophy and hyperplasia due to abnormal thyroid-stimulating antibodies (TSH-RAbs) that bind to TSH receptor sites and produce a disproportionate and prolonged effect. The onset is abrupt, but remissions and exacerbations are not infrequent.
Hyperthyroidism is usually more severe than in secondary thyrotoxicosis but cardiac failure is rare. Manifestations of thyrotoxicosis not due to hyperthyroidism e.g. orbital proptosis, ophthalmoplegia and pretibial myxoedema, may occur in primary thyrotoxicosis.

Toxic nodular goitre
A simple nodular goitre is present for a long time before the hyperthyroidism, usually in the middle-aged or elderly. The syndrome is that of secondary thyrotoxicosis. In secondary thyrotoxicosis the goitre is nodular.
The onset is insidious and may present with cardiac failure or atrial fibrillation.
It is characteristic that the hyperthyroidism is not severe. Eye signs other than lid lag and lid spasm (due to hyperthyroidism) are very rare.

Toxic nodule
A toxic nodule is a solitary overactive nodule, which may be part of a generalised nodularity or a true toxic adenoma. It is autonomous and its hypertrophy and hyperplasia are not due to TSH-RAb.
TSH secretion is suppressed by the high level of circulating thyroid hormones and the normal thyroid tissue surrounding the nodule is itself suppressed and inactive.

Diagnosis of thyrotoxicosis
Most cases are readily diagnosed clinically.
Hyperthyroidism is confirmed biochemically by raised level of circulating thyroid hormones and decrease TSH level. A TRH test is rarely indicated.
T3 thyrotoxicosis is diagnosed by estimating the free T3.
It should be suspected if the clinical picture is suggestive but routine tests of thyroid function reveal a normal T4 but suppressed TSH.
A thyroid scan is required to diagnose an autonomous toxic nodule and differentiate it from a dominant swelling in a toxic multinodular goitre.

Principles of treatment of thyrotoxicosis
Non-specific measures are rest and sedation.