25,729 articles
Thrombus
Thrombus (plural thrombi): a blood clot forming inside a vein, artery, or heart; if it breaks loose it becomes an embolus. Framed by Virchow's triad of hypercoagulability, stasis, and endothelial injury; causes DVT, pulmonary embolism, ischemia, and stroke.
Thumb
Thumb (pollex): the first digit, with two phalanges and a saddle-shaped trapeziometacarpal joint enabling opposition and pinch. Covers anatomy, evolution, basal joint arthritis, fractures, and reconstruction.
Thunderclap headache
Thunderclap headache: severe headache peaking within about a minute, a red flag for subarachnoid hemorrhage; term coined by Day and Raskin (Lancet 1986); evaluated with CT within 6 hours, then lumbar puncture or CT angiography.
Thygeson superficial punctate keratitis
Thygeson superficial punctate keratitis (TSPK), also called Thygeson's superficial punctate keratopathy, is a rare chronic bilateral corneal epitheliopathy with recurrent gray-white intraepithelial opacities, unknown cause, HLA-DR3 association, and corticosteroid-responsive flares.
Thymalfasin
Thymalfasin, sold as Zadaxin, is a synthetic thymosin alpha 1 peptide approved for hepatitis B in China and other countries, but not by the FDA.
Thymectomy
Thymectomy is surgical removal of the thymus gland, performed in myasthenia gravis to improve weakness or remove a thymoma (about 10% of MG patients). The 2016 MGTX randomized trial confirmed benefit plus prednisone; MuSK-antibody MG is excluded.
Thymic carcinoma
Thymic carcinoma (WHO type C) is a highly malignant thymic epithelial tumor with cytologic atypia resembling carcinomas of other organs. About 1% of anterior mediastinal tumors; 5-year survival 30-50%; treated with resection and platinum chemotherapy.
Thymic cyst
Thymic cyst: fluid-filled sac within thymic tissue in the mediastinum or neck; congenital (unilocular) or acquired (multilocular, linked to inflammation or tumors). Benign, often asymptomatic; CT attenuation can mimic solid masses, MRI clarifies, surgery or surveillance.
Thymic hyperplasia
Thymic hyperplasia: benign enlargement or lymphoid follicular proliferation of the thymus, including true, rebound, follicular, and LESA-like types; linked to myasthenia gravis and Graves disease, distinguished from thymoma by chemical shift MRI.
Thymic involution
Thymic involution is the age-related atrophy of the thymus, replacing T-cell-producing epithelial tissue with fat from early life onward, reducing naive T cell output and raising infection, cancer, and autoimmune risk; partially reversible experimentally but no approved therapy.
Thymic neuroendocrine carcinoma
Thymic neuroendocrine carcinoma is a rare, aggressive tumor of the thymus, accounting for about 0.4% of carcinoid tumors; surgery is the mainstay treatment, with 5-year survival of 68%.
Thymic neuroendocrine tumor
Thymic neuroendocrine tumor (thymic carcinoid, TNET): rare malignant neuroendocrine neoplasm of the thymus in the anterior mediastinum; male-predominant, linked to MEN1 and Cushing syndrome, treated mainly by surgery.
Thymoma
Thymoma: an epithelial tumor of the thymus (thymic epithelial tumor, TET), WHO types A, AB, B1-B3; anterior mediastinal mass, 0.13/100,000 incidence, strongly linked to myasthenia gravis, treated mainly by surgery.
Thymoma-hypogammaglobulinemia syndrome
Thymoma-hypogammaglobulinemia syndrome, also called Good syndrome, is a rare acquired immunodeficiency of adults combining a thymoma with low immunoglobulins, low B cells, and increased infections.
Thymopentin
Thymopentin (TP-5), Arg-Lys-Asp-Val-Tyr, a synthetic pentapeptide matching amino acids 32-36 of thymopoietin; immunomodulator enhancing T-cell production, studied in HIV, tuberculosis, and eczema, never FDA-approved.
Thymosin
Thymosin: family of thymus-derived polypeptide hormones named in 1966 by Goldstein and White. Key members are thymosin alpha-1 (Zadaxin, sepsis and hepatitis studies, not FDA-approved) and thymosin beta-4 (actin-binding, wound healing, WADA-prohibited).
Thymulin
Thymulin, formerly known as FTS, is a zinc-dependent nonapeptide hormone produced by thymic epithelial cells that promotes T cell differentiation, discovered by French immunologists in the 1970s.
Thymus
Thymus: bilobed primary lymphoid organ in the superior mediastinum where T cells mature and undergo selection; undergoes involution from puberty; linked to myasthenia gravis, DiGeorge syndrome, and thymectomy.
Thymus histology
Thymus histology is the microscopic structure of the thymus, a two-lobed lymphoepithelial organ above the heart, organized into a thymocyte-packed cortex and a paler medulla containing Hassall's corpuscles.
Thymus transplantation
Thymus transplantation (cultured thymus tissue implantation, CTTI, RETHYMIC) treats congenital athymia by implanting cultured donor thymus slices into quadriceps muscle; FDA approved October 8, 2021, available at Duke and Great Ormond Street Hospital, 77% one-year survival.
Thyroid
Thyroid: butterfly-shaped endocrine gland in the neck producing T4 and T3 under TSH control; depends on iodine; hypothyroidism affects about 4.6% of Americans age 12 and older.
Thyroid cancer
Thyroid cancer: malignancy of the thyroid gland with four main types (papillary, follicular, medullary, anaplastic). About 44,020 US cases in 2025; papillary and follicular forms are usually curable, anaplastic is nearly always fatal.
Thyroid disease
Thyroid disease: group of disorders of the butterfly-shaped neck gland, including hypothyroidism (Hashimoto's), hyperthyroidism (Graves'), nodules, and cancer; diagnosed mainly by TSH blood tests.
Thyroid ectopia
Thyroid ectopia (ectopic thyroid, lingual thyroid): a developmental anomaly with thyroid tissue outside the anterior neck, most often at the tongue base; causes about two-thirds of thyroid dysgenesis and congenital hypothyroidism, female predominance 2:1.
Thyroid feedback quantile-based index
The thyroid feedback quantile-based index (TFQI) is a calculated measure of impaired pituitary sensitivity to free thyroxine, proposed in Diabetes Care in 2018 and ranging from −1 to 1.
Thyroid function tests
Thyroid function tests (TFTs) are blood tests measuring TSH, free T4, and free T3 to diagnose and monitor thyroid disorders; TSH is the first-line test, with reflex free T4 added when TSH is abnormal.
Thyroid hemiagenesis
Thyroid hemiagenesis (THA, ORPHA:95719) is a rare congenital absence of one thyroid lobe, usually the left (about 80% of cases), affecting roughly 0.02–0.2% of people, more often females, and usually asymptomatic.
Thyroid hormones
Thyroid hormones: T4 (thyroxine) and T3 (triiodothyronine), iodine-containing hormones from the thyroid gland regulating metabolism, growth, and brain development, activated locally by deiodinases and replaced clinically with levothyroxine.
Thyroid hypoplasia
Thyroid hypoplasia (congenital thyroid hypoplasia) is incomplete development of the thyroid gland in newborns, one form of thyroid dysgenesis causing permanent congenital hypothyroidism, usually sporadic, detected by newborn screening and treated with levothyroxine.
Thyroid lymphoma
Thyroid lymphoma is a rare B-cell non-Hodgkin lymphoma arising in the thyroid gland, accounting for about 1% to 5% of thyroid cancers and usually occurring in older women.