Hyperthyroidism may be referred to as "thyrotoxicosis" or toxic levels of thyroid hormone being produced. Similar to hypothyroidism, cases of hyperthyroidism may be broadly categorized as primary, secondary, and tertiary, as summarized in Table 6.
Primary hyperthyroidism relates to the thyroid gland producing large amounts of hormone due to either uncontrolled growth of hormone-producing functional tissue or by way of an autoimmune process that interferes with the normal feedback control.
Secondary hyperthyroidism may be attributed to an over-stimulation of the thyroid. This may be due to increased production of TSH from the pituitary gland or a TSH-secreting tumor.
Tertiary hyperthyroidism occurs from the overproduction of thyrotropin-releasing hormone (TRH) from the hypothalamus or a TRH-secreting tumor. It is rarer than secondary hyperthyroidism.
Table 6. Types of Hyperthyroidism.| Type | Origin | Cause |
| Primary | Thyroid | Thyroid nodulesThyroid adenomaGraves’ diseaseThyroiditis |
| Secondary | Pituitary | CarcinomaTSH-secreting tumors |
| Tertiary | Hypothalamus | TRH-secreting tumorsVery rare |
