The clinical manifestations of hyperthyroidism are largely independent of its cause (see "Disorders that cause hyperthyroidism"). However, the disorder that causes hyperthyroidism may have other effects. In particular, Graves' disease, the most common cause of hyperthyroidism, causes unique problems that are not related to the high serum thyroid hormone concentrations. These include Graves' ophthalmopathy and infiltrative dermopathy (localized or pretibial myxedema). Most patients with Graves' hyperthyroidism have a diffuse goiter, but so do patients with other, less common causes of hyperthyroidism such as painless thyroiditis and thyrotropin (TSH)-secreting pituitary tumors.
The major clinical manifestations of hyperthyroidism (thyrotoxicosis) will be briefly reviewed here. More detailed discussions of its effects on specific organ systems as well as the diagnostic approach to patients with hyperthyroidism are discussed separately. (See "Diagnosis of hyperthyroidism".)
The skin is warm (and may rarely be erythematous) in hyperthyroidism due to increased blood flow; it is also smooth because of a decrease in the keratin layer . Other changes include:
●Sweating, which increases due to increased calorigenesis; this is often associated with heat intolerance
●Onycholysis (loosening of the nails from the nail bed, Plummer's nails) and softening of the nails