Thyrotoxicosis is the clinical syndrome of hypermetabolism caused by elevated serum thyroid hormone levels. The term hyperthyroidism is used to designate a prolonged increase in the biosynthesis and secretion of thyroid hormones originating from the thyroid gland. Therefore, the terms "thyrotoxicosis" and hyperthyroidism are not identical. Although many patients with thyrotoxicosis have hyperthyroidism, others such as those whose thyrotoxicosis is due to thyroiditis or exogenous administration of thyroxine do not have it.
Clinical manifestations of the disease are largely independent of the etiology. However, several characteristics drive the clinician to the cause of the disease. Such characteristics include duration of the disease, the size and texture of the thyroid, the presence or absence of extrathyroidal manifestations, such as e.g. Graves' disease ophthalmopathy. An attempt should always be made to determine the cause of thyrotoxicosis in all patients by clinical examination and laboratory testing because knowledge of the cause determines prognosis and treatment. The causes of thyrotoxicosis can be classified based on the presence or absence of hyperthyroidism and based on their frequency of occurrence. Graves' disease is the most common, accounting for approximately 60% – 90% of all cases of thyrotoxicosis. Most of the remaining causes involve polynodular toxic goiter and toxic adenoma as well as various types of thyroiditis. Apart from thyrotoxicosis resulting from exogenous administration of thyroxine, all other causes are rare.
The most frequent subjective symptoms and findings of the disease are reported in the table below. None of the symptoms of the disease are specific. Usually, the combination of several of them in the same patient advocates the presence of the disease in that patient. The frequency and severity of subjective symptoms and clinical findings varies from patient to patient. Some patients report few symptoms and clinical signs and others more. However, there are cases where specific clinical findings also determine the cause of thyrotoxicosis, as shown in the Table:
| Causes of thyrotoxicosis |
| Common causes |
| Thyrotoxicosis with hyperthyroidism |
| N. Graves' |
| Toxic multinodular goiter |
| Toxic adenoma |
| Thyrotoxicosis without hyperthyroidism |
| Inflammatory causes: Silent or subacute thyroiditis |
| Extrathyroidal source thyr. Hormones: Exogenous intake of thyroxine |
| Unusual causes |
| Thyrotoxicosis with hyperthyroidism |
| Hypersecretion of TSH |
| Superindirect gravidarum |
| Thyroid cancer |
| Struma ovarii |
| Medicines: iodine, lithium |
| Thyrotoxicosis without hyperthyroidism |
| Inflammatory diseases |
| Medicines that cause thyroiditis (Amiodarone, Interferon α) |
| Metastatic thyroiditis |
| Clinical manifestations of common causes of thyrotoxicosis | |
| Symptoms and findings | Cause |
| Diffuse goiter | Graves' – latent thyroiditis |
| Multinodular goiter | Thyroid autonomy |
| Contralateral nodular goiter | Thyroid autonomy |
| Pain, thyroid tenderness | Subacute thyroiditis |
| Eye disease | Graves' |
| Localized (tibial) myxedema | Graves |
GRADUATE COURSES IN ENDOCRINOLOGY AND DIABETES- DEPARTMENT OF ENDOCRINOLOGY DIABETES AND METABOLISM OF EVANGELISMOS GENERAL HOSPITAL OF ATHENS- 2004
