- from: endocrinology
thyroid disorders
- Common Diagnostic Tests in Thyroid Disorders
- Specialized Diagnostic Tests in Thyroid Disorders
- hypothyroidism
- hyperthyroidism
- nonthyroidal illness (sick euthyroid syndrome)
- thyroid storm
- amiodarone and thyroid disease
- thyrotoxic periodic paralysis (TPP)
- thyroid cancer
- Washington Manual Thyroid Disorders
FIGURE 5.3: Hypothalamic–pituitary–thyroid axis. Shown is the hypothalamic–pituitary–thyroid axis, which regulates the production of thyroid hormones. The enzyme 5′ iodinase converts the biologically inactive thyroxine (T4) to the active form of thyroid hormone, triiodothyronine (T3). Conversion of T4 → T3 can be inhibited by environmental conditions (illness, starvation) or medications (propylthiouracil [PTU], propranolol). T4 can also be converted to reverse T3 (rT3), which is a biologically inactive metabolite of thyroxine. Green arrows indicate stimulatory actions, and red lines indicate inhibitory actions. Abbreviations: TRH, thyrotropin-releasing hormone; TSH, thyroid-stimulating hormone; T4, thyroxine; T3, triiodothyronine; rT3, reverse triiodothyronine.