Life and health

HDAC2

HDAC2 (histone deacetylase 2, gene ID 3066, 6q21) is a human class I zinc-dependent histone deacetylase acting in NuRD, Sin3A, CoREST, and MiDAC repressor complexes; 85% identical to HDAC1, overexpressed in cancers, implicated in memory impairment, and targeted by HDAC1/2-selective inhibitors.

HDAC3

HDAC3 (histone deacetylase 3, gene ID 8841) is a class I zinc-dependent deacetylase whose enzymatic activity is licensed by NCoR/SMRT corepressor complexes; it regulates metabolism, circadian rhythms, inflammation, and is a drug target.

HDAC4

HDAC4 (histone deacetylase 4) is a class IIa human enzyme on chromosome 2 that shuttles between nucleus and cytoplasm, represses MEF2 and Runx2 transcription, and is required for normal development.

HDAC5

HDAC5 (histone deacetylase 5, NY-CO-9) is a class IIa human deacetylase on chromosome 17q21.31, largely scaffold-like without HDAC3, regulated by phosphorylation-dependent nuclear shuttling, implicated in heart, neurons, and cancer.

HDAC6

HDAC6 (histone deacetylase 6, EC 3.5.1.98) is the predominantly cytoplasmic class IIB HDAC with two catalytic domains and a ubiquitin-binding BUZ domain; it deacetylates α-tubulin, HSP90, and cortactin, and is targeted by inhibitors such as ricolinostat in cancer, CMT, and HFpEF trials.

HDAC9

HDAC9 (histone deacetylase 9) is a human class IIa HDAC gene at 7p21.1 encoding a 1,069-aa MEF2-interacting transcriptional repressor with very weak catalytic activity; a GWAS stroke risk locus linked to large-vessel ischemic stroke and cancer.

HDacro trial

HDacro trial (NCT00461149), Federico II University Naples, Colao: 24-month open-label phase 4 study of octreotide-LAR dose escalation (20 to 40 mg q28d) as first-line acromegaly therapy, achieving 80.3% biochemical control and 68% tumor shrinkage.

HDLBP

HDLBP, also called vigilin (VIGLN_HUMAN), is a human RNA-binding protein gene on 2q37.3 encoding 1268 amino acids with 14-15 KH domains, involved in cholesterol transport, translation, heterochromatin, cancer, and viral replication.

He Jiankui (贺建奎)

He Jiankui (贺建奎), Chinese biophysicist formerly at SUSTech, Shenzhen, announced the first CRISPR-edited babies (CCR5, twins Lulu and Nana) in 2018; jailed three years in 2019, released 2022, now seeking a research comeback.

Head

Head: the uppermost part of the human body, containing the brain in its 22-bone skull (cranium), the face, and sensory organs; divided into neurocranium and viscerocranium, joined by sutures.

Head and neck cancer

Head and neck cancer: group of cancers of the mouth, throat, larynx, sinuses, nasal cavity, and salivary glands, mostly squamous cell carcinomas; driven by tobacco, alcohol, and HPV, with rising HPV-related oropharyngeal incidence.

Head drop

Head drop (dropped head syndrome, 首下がり症候群; ICD-11 MB45.3): chin-on-chest posture from neck extensor muscle weakness, caused by ALS, myasthenia gravis, parkinsonism, or isolated neck extensor myopathy; treated medically or surgically.

Sep 29, 2026

Head impulse test

The head impulse test, also called the head thrust test, is a bedside maneuver that assesses the vestibulo-ocular reflex to detect unilateral inner-ear balance dysfunction.

Head injury

Head injury is trauma to the scalp, skull, or brain, excluding the face and jaws. Also called traumatic brain injury when the brain is affected; graded mild, moderate, or severe by the Glasgow Coma Scale, with primary and secondary injury phases.

Head louse

Head louse (Pediculus humanus capitis), a bloodsucking insect parasite of the human scalp, spread by head-to-head contact, causing pediculosis capitis; harmless disease-wise, treated with pediculicides such as permethrin or occlusive agents.

Head Movements

Head movements: voluntary or involuntary motion of the head in humans and animals (MeSH D019416). Covers gaze stabilization via the vestibulo-ocular reflex, head impulse testing, active versus passive movement effects, and nonverbal communication roles.

Head Protective Devices

Head protective devices are helmets and hard hats that absorb impact energy to reduce head injury in military, industrial, road, and sport settings, spanning steel M1 combat helmets, ANSI Z89.1 and ISO 3873 industrial standards, and rotational-protection technologies like MIPS.

Head transplant

Head transplant, also called whole-body transplantation, is an experimental procedure attaching a living head with its brain to a donor body. Performed partially in dogs, mice, and Robert White's 1970 rhesus monkeys (nine-day survival); proposed for humans by Sergio Canavero, with a 2017 cadaver rehearsal, but spinal cord fusion remains unsolved.

Sep 29, 2026

Head-down tilt

Head-down tilt is a positioning method with the head below the feet, used in space medicine to simulate weightlessness, typically at -6° for days to weeks.

Head-related transfer function

Head-related transfer function (HRTF): direction-dependent acoustic filter of sound by a listener's head, pinnae, and torso, measured at the ear canal entrance; listener-specific like a fingerprint, basis of binaural VR audio, carrying ITD, ILD, and spectral localization cues.

Headache

Headache: pain in the head or upper neck; headache disorders include primary types (migraine, tension-type, cluster), secondary types such as medication-overuse headache, and affect about 40% of the global population.

Heads of Medicines Agencies

Heads of Medicines Agencies (HMA): network of heads of national medicines regulators for human and veterinary products in the EEA, founded 1996, 30 countries, partner of EMA, joint EMANS strategy to 2028.

Healdia

Healdia (type species Healdia simplex) is an extinct genus of small ostracod crustaceans in the family Healdiidae, named by Roundy in 1926 from Carboniferous Texas, with a fossil record from the Paleozoic into the Early Jurassic.

Healed venous leg ulcer

Healed venous leg ulcer: a venous stasis ulcer whose skin has fully re-epithelialized. Recurrence reaches 50-70% within five years; prevention relies on compression stockings, leg elevation, and ablation of superficial venous reflux.

Healing

Healing, or wound healing, is the biological repair process of hemostasis, inflammation, proliferation, and remodeling; impaired healing yields chronic wounds treated with debridement, dressings, compression, and advanced therapies.

HEALIVE

HEALIVE (孩尔来福) is Sinovac's inactivated hepatitis A vaccine using the TZ84 strain in 2BS human diploid cells; China-approved 2002, WHO-prequalified 2017, two-dose pediatric 250 U and adult 500 U schedule.

Health

Human health: the WHO-defined state of complete physical, mental and social well-being, not merely absence of disease. Covers determinants (social, environmental, commercial), measurement, health assessments, and 2026 global SDG status.

Health administration

Health administration: leadership and management of healthcare organizations by medical and health services managers (healthcare executives). Covers MHA/MBA/FACHE credentials, 640,400 US jobs at $123,860 median pay, 15–30% administrative cost share, and multi-payer versus single-payer differences.

Health and appearance of Michael Jackson

Health and appearance of Michael Jackson: the pop star's vitiligo and lupus diagnoses, 1984 Pepsi scalp burns, depigmentation with Benoquin, plastic surgery, and his 2009 death and autopsy findings.