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Hypnic headache
Hypnic headache, or "alarm clock" headache, is a rare primary headache disorder first described by Raskin in 1988: sleep-only attacks waking patients, lasting 15 minutes to 4 hours, treated with lithium, caffeine, melatonin, or indomethacin.
Hypnic jerk
Hypnic jerk, also called sleep start or hypnagogic jerk: a brief involuntary myoclonic muscle contraction at sleep onset, stage N1, with falling sensation; affects about 70% of people, triggered by stress, caffeine, and sleep deprivation.
Hypnopompic hallucinations
Hypnopompic hallucinations are vivid, often visual, dream-like hallucinations that occur on waking from sleep. They are common, and frequent episodes, especially with sleep paralysis, can point to narcolepsy.
Hypnosis
Hypnosis, also known as hypnotism, is a state of concentrated attention with reduced awareness of surroundings and heightened responsiveness to suggestion, first named in 1843.
Hypnotherapy
Hypnotherapy is the therapeutic use of hypnosis via induction and suggestion. Rooted in Mesmerism, named by Braid in 1843; best evidence for gut-directed IBS treatment, weaker for smoking cessation.
Hypnotic
Hypnotic: sleep-inducing drug class for insomnia, also called sedative-hypnotics; spans barbiturates, benzodiazepines, Z-drugs, melatonin agonists, and orexin antagonists, with CBT-I preferred first-line.
HYPNOVRNEO trial
The HYPNOVRNEO trial was a randomized controlled trial in Rennes, France, testing whether six 10-minute virtual reality hypnosis sessions during work breaks reduced stress and compassion fatigue among NICU nurses.
HYPO-5 trial
HYPO-5 (NCT05786742) is a phase 1-2 CHU de Québec trial comparing 25 Gy/5-fraction ultra-hypofractionated prostate radiotherapy plus a 15 Gy HDR brachytherapy boost against moderately hypofractionated schedules, reporting interim safety and biochemical control.
Hypo-OPRA trial
Hypo-OPRA (NCT06991465) is a phase II single-arm McGill trial testing 25 Gy in 5 fractions plus a boost to 35 Gy with FOLFOX or capecitabine for rectal preservation in locally advanced rectal adenocarcinoma.
Hypoactive sexual desire disorder
Hypoactive sexual desire disorder (HSDD), also called female sexual interest/arousal disorder in DSM-5, is persistent low sexual desire causing marked distress. Covers diagnosis, prevalence (8–10% of women), mechanisms, flibanserin, bremelanotide, testosterone, and controversy.
Hypoalbuminemia
Hypoalbuminemia, low serum albumin below 35 g/L, is a common hospital finding driven mainly by inflammation and protein loss, a strong mortality predictor, and a poor nutrition marker; albumin infusion has few supported indications.
Hypoaldosteronism
Hypoaldosteronism (ICD-11 5A73) is deficient aldosterone production or action, causing hyperkalemia, hyponatremia, and acidosis. Forms include hyporeninemic hypoaldosteronism, CYP11B2 aldosterone synthase deficiency, and pseudohypoaldosteronism; treated with fludrocortisone or sodium supplementation.
Hypocalcemia
Hypocalcemia, or low blood calcium, is an abnormally low serum calcium level caused by hypoparathyroidism, vitamin D deficiency, or kidney disease, treatable with calcium and vitamin D.
Hypocalcemic vitamin D-dependent rickets
Hypocalcemic vitamin D-dependent rickets (VDDR type 1, VDDR1A/VDDR1B; 1-alpha-hydroxylase deficiency) is a rare autosomal recessive disorder of vitamin D activation causing infantile hypocalcemia and rickets, treated with calcitriol.
Hypocalcemic vitamin D-resistant rickets
Hypocalcemic vitamin D-resistant rickets (HVDRR, VDDR2A, OMIM 277440) is a rare autosomal recessive rickets caused by VDR gene mutations, causing calcitriol resistance, hypocalcemia, elevated calcitriol, and alopecia in about half to two-thirds of patients.
Hypocalciuria
Hypocalciuria (low urinary calcium; ICD-11 MF98.3), also called low urine calcium. Key causes: familial hypocalciuric hypercalcemia (CASR, GNA11, AP2S1 mutations), thiazides, lithium, vitamin D deficiency; CCCR <0.01 suggests FHH over primary hyperparathyroidism.
Hypocapnia
Hypocapnia, also called hypocarbia, is an arterial CO2 partial pressure below 35 mm Hg (normal 35-45), usually from hyperventilation, causing respiratory alkalosis and cerebral vasoconstriction; transiently lifesaving for intracranial hypertension but harmful when prolonged.
Hypochondriasis
Hypochondriasis: persistent preoccupation with having serious illness despite reassurance; DSM-IV somatoform diagnosis, split by DSM-5 into illness anxiety disorder and somatic symptom disorder, retained in ICD-11.
Hypochondroplasia
Hypochondroplasia is an uncommon hereditary disorder of skeletal development caused by mutations in the FGFR3 gene, producing short stature with disproportionately short limbs, typically milder than achondroplasia.
Hypochromic anemia
Hypochromic anemia (historically chlorosis): anemia with abnormally low red cell hemoglobin concentration (MCHC < 32 g/dL), usually microcytic; most often iron deficiency, but thalassemia, sideroblastic anemia, and lead poisoning must be distinguished by iron studies.
Hypocomplementemic urticarial vasculitis
Hypocomplementemic urticarial vasculitis (HUV, McDuffie syndrome, HUVS) is a rare anti-C1q immune complex small vessel vasculitis with chronic urticaria, low C1q/C3/C4, arthritis, ocular, renal, and pulmonary involvement.
Hypodermic needle
Hypodermic needle: hollow stainless steel tube on a Luer hub for injecting medication or aspirating fluid below the skin; FDA Class II (880.5570), ISO 7864 single-use standard, sizes 0.18-3.4 mm, invented from Rynd's 1844 needle and Wood/Pravaz 1853 syringes.
Hypodermoclysis
Hypodermoclysis, or subcutaneous fluid infusion, rehydrates mildly to moderately dehydrated patients, especially older adults and palliative care patients, when venous access is difficult; about 3 L daily at two sites.
Hypodontia-dysplasia of nails syndrome
Hypodontia-dysplasia of nails syndrome, also known as Witkop syndrome or tooth and nail syndrome, is a rare autosomal dominant ectodermal dysplasia causing missing permanent teeth and dysplastic nails, first described in 1965.
Hypogastric plexus
The hypogastric plexus is a network of nerve fibers in the pelvis, divided into superior and inferior parts, that supplies autonomic innervation to the bladder, rectum, and reproductive organs.
Hypoglossal nerve
Hypoglossal nerve (cranial nerve XII): pure motor nerve from the medulla's hypoglossal nucleus, exiting via the hypoglossal canal, supplying all tongue muscles except palatoglossus; lesions deviate the tongue toward the lesion.
Hypoglossal nerve stimulation
Hypoglossal nerve stimulation is a surgically implanted therapy that moves the tongue forward during sleep to treat obstructive sleep apnea in adults who cannot use CPAP.
Hypoglossia-hypodactyly syndrome
Hypoglossia-hypodactyly syndrome, also called Hanhart syndrome or aglossia-adactylia, is a rare congenital condition combining an underdeveloped tongue, a small lower jaw, and limb defects ranging from missing finger and toe bones to absent digits or limbs.
Hypoglycaemia unawareness
Hypoglycaemia unawareness, or impaired awareness of hypoglycaemia, is loss of autonomic warning symptoms of low blood glucose in insulin-treated diabetes, driven by recurrent hypoglycaemia via HAAF, raising severe hypoglycaemia risk about six-fold.
Hypoglycemia
Hypoglycemia, also known as low blood sugar or glucopenia, is a blood glucose concentration below 70 mg/dL (3.9 mmol/L); it is common in people treated with insulin and can cause confusion, seizures, or coma.