Human health and medicine

Ovarian Reserve

Ovarian reserve, the number of oocytes remaining in the ovaries, is measured with AMH, antral follicle count, and FSH; it predicts IVF oocyte yield well but reproductive potential poorly, and should not be used as a fertility test.

Ovarian stimulation protocol

An ovarian stimulation protocol is a regimen of hormonal medications used in assisted reproduction to develop multiple ovarian follicles before egg retrieval for IVF or ICSI.

Ovarian suppression

Ovarian suppression, also called ovarian function suppression, is a treatment that stops the ovaries from producing estrogen, used to treat hormone-receptor-positive breast cancer in premenopausal women.

Ovarian tissue cryopreservation

Ovarian tissue cryopreservation is a fertility preservation technique that freezes ovarian tissue for later reimplantation, restoring hormones and fertility; more than 300 live births have been reported since 2004.

Ovarian tissue transplantation

Ovarian tissue transplantation is a fertility-preservation procedure in which cryopreserved ovarian cortex is reimplanted to restore ovarian hormone function and fertility, yielding over 300 reported live births.

Ovarian torsion

Ovarian torsion (adnexal torsion): twisting of the ovary around the infundibulopelvic and utero-ovarian ligaments, cutting blood flow; a gynecological emergency treated by laparoscopic detorsion with ovarian preservation, peak age 29–34.

Ovary

Ovary: paired female gonad producing oocytes and the hormones estrogen and progesterone; almond-sized organs beside the uterus; follicles, ovulation, corpus luteum, menopause, and disorders such as PCOS and ovarian cancer.

Oveporexton

Oveporexton (TAK-861, brand Orzeyful) is Takeda's oral orexin receptor 2-selective agonist for narcolepsy type 1; FDA approved August 2026 after positive phase 2b and phase 3 trials showing improved wakefulness, sleepiness, and cataplexy.

OVER trial

OVER trial (Open Versus Endovascular Repair Trial, NCT00094575): US Veterans Affairs randomized trial of 881 veterans comparing endovascular versus open abdominal aortic aneurysm repair; lower perioperative mortality with EVAR, no long-term survival difference.

Over-the-counter drug

An over-the-counter (OTC) drug, also called a nonprescription drug, is a medicine consumers can buy and use without a prescription, such as pain relievers, antacids, and sunscreens.

Overactive bladder

Overactive bladder (OAB), or urgency with frequency and nocturia with or without urgency incontinence, affects over 30 million Americans aged 40+. Treated with bladder training, antimuscarinics, beta-3 agonists like mirabegron, then botulinum toxin or neuromodulation.

OVERCOME-TBI study

OVERCOME-TBI (NCT06927063) is a prospective observational study at Turku University Hospital following up to 160 TBI patients from the TBIcare and PACoS-TBI cohorts with MRI, PET, blood biomarkers, and gut microbiome profiling at chronic post-injury time points.

Overdiagnosis

Overdiagnosis: diagnosing conditions that would never have harmed a patient, especially in cancer screening; MeSH-defined, estimated at 17-38% in randomized screening trials, causing overtreatment harm.

Overhydrated hereditary stomatocytosis

Overhydrated hereditary stomatocytosis (OHST, hydrocytosis, OMIM 185000) is a rare autosomal dominant hemolytic anemia caused by RHAG mutations, with cation-leaky overhydrated stomatocytes, absent stomatin, and contraindicated splenectomy.

Overlap myositis

Overlap myositis (non-specific myositis, ORPHA:206572) is a subtype of idiopathic inflammatory myopathy combining myositis with clinical or autoantibody features of another connective tissue disease, common in adult women, with frequent interstitial lung disease.

Overlapping Surgery

Overlapping surgery: one primary attending surgeon runs two operating rooms with staggered critical portions, distinct from prohibited concurrent surgery; CMS-approved, ethically debated, and studied across 200,000+ patients.

Overlay Denture

Overlay denture (overdenture): removable dental prosthesis built over natural tooth roots or implants, per MeSH D003828. Tooth-supported and implant-supported types; attachments include ball, bar, locator, magnet, telescopic; two-implant mandibular IOD is standard since 2002.

Overtreatment

Overtreatment is the excessive provision of medical treatment or preventive procedures, typically arising from overdiagnosis, and is a major component of medical overuse alongside it.

Overvalued ideas

Overvalued ideas (Ueberwertige Idee), coined by Carl Wernicke in 1892, are ego-syntonic, emotionally amplified beliefs dominating behavior, less intense than delusions; ICD-11 code MB26.6, linked to anorexia, BDD, OCD, and forensic threat assessment.

Overweight

Overweight: excess body weight relative to height, defined as BMI 25–29.9 in adults (WHO: ≥25). Affects 2.6 billion adults in 2024; raises risk of cardiovascular disease, diabetes, and cancers.

Overweight in adults

Overweight in adults: BMI 25–29.9 kg/m² (obesity ≥30) by WHO definition. 45% of adults (2.6 billion) were overweight in 2024, up from 25% in 1990; diagnosis now pairs BMI with waist measures.

Overwhelming post-splenectomy infection

Overwhelming post-splenectomy infection (OPSI), or post-splenectomy sepsis, is fulminant sepsis in asplenic or hyposplenic people, mainly from Streptococcus pneumoniae and other encapsulated bacteria, progressing within 24-48 hours with 50-70% mortality if untreated.

Ovine pulmonary adenocarcinoma

Ovine pulmonary adenocarcinoma (jaagsiekte, sheep pulmonary adenomatosis) is a contagious lung cancer of sheep caused by jaagsiekte sheep retrovirus (JSRV), a betaretrovirus whose Env protein is an oncoprotein; endemic worldwide except Australia and New Zealand, with no vaccine.