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alopecia: [Gk, alopex, fox (mange)], partial or complete lack of hair resulting from various disorders or conditions

alopecia androgenetica: [Gk, alopex, fox (mange) + Gk, andros + genein, to produce], the medical name for male or female pattern baldness

alopecia areata: [Gk, alopex, fox (mange) + L, area, open space], hair loss in sharply defined patches

5 alpha-reductase: the enzyme necessary to convert testosterone to dihydrotestosterone (DHT). Type 1 5-alpha reductase is found primarily in the skin and type 2 5-alpha reductase is found primarily in the prostate

anagen: [Gk, ana, up, again + genein, to produce], the growing phase of hair, which shows great variation, ranging from two to six or more years

androgen: [Gk, andros + genein, to produce], any steroid hormone that increases male characteristics

apoptosis: [Gk, apo, separation + ptosis, falling], programmed cell death

azelaic acid: a naturally occurring saturated dicarboxylic acid with the chemical name of 1,7-heptanedicarboxylic acid and a molecular weight of 188.22. Azelaic acid is a dietary component of whole grain cereals and animal products. Azelaic acid (0.1 to 3.0 mmol/l) has been shown to produce a competitive concentration dependent inhibition of 5-alpha reductase activity in human skin and is used topically to inhibit the synthesis of DHT in the scalp

biopsy: [Gk, bios, life + opsis, view], the removal of a small piece of living tissue from an organ or other part of the body for microscopic examination

castration: [L, castrare, to castrate], the surgical excision of one or both testicles or ovaries

catagen: [Gk, kata, down, under + genein, to produce], the short transition phase of the hair growth cycle, lasting two to three weeks

clone: [Gk, klon, a plant cutting], a group of genetically identical cells or organisms derived from a single common cell

crown: [L, corona, an encircling structure], the upper part of an organ or structure, such as the top of the head

dermatology: [Gk, derma, skin + logos, science], the study of the skin, including the anatomy, physiology, and pathology of the skin and the diagnosis and treatment of skin disorders

dermis: [Gk, derma, skin], the layer of the skin, just below the epidermis, consisting of papillary and reticular layers and containing blood and lymphatic vessels, nerves and nerve endings, glands and hair follicles

DHT: acronym for dihydrotestosterone. Classified as a 'sex hormone', there is no well delineated relationship to the levels of DHT and libido or sexual activity. Other than promoting hair growth on the face and upper pubis (but having just the opposite effect on the scalp), the role of DHT in the adult human male is a mystery.

dutasteride: a medication currently under development by Glaxo-Wellcome, which is a dual inhibitor of the 5-alpha reductase enzymes responsible for converting testosterone to DHT

effluvium: [L, effluvium, a flowing out], an outflow, which may pertain to sudden, severe hair shedding

epidermis: [Gk, epi, on or upon + derma, skin], the superficial, avascular, layers of the skin, made up of an outer, dead cornified portion and a deeper, living, cellular portion. Altogether, these layers are between 0.5 to 1.1 mm

estrogen: [Gk, oistros, gadfly + genein, to produce], one of a group of hormonal steroid compounds that promote the development of female secondary sex characteristics

etiology: [Gk, aitia, cause + logos, science], the cause of a disease

finasteride: the generic name for Propecia and Proscar, which are drugs that bind with the type 2 5-alpha reductase enzyme and reduce the amount of DHT in the prostate and serum

follicle: [L, folliculus, small bag], a pouchlike depression, such as the hair follicles within the dermis that enclose the hair roots

frontal hairline: [L, frons, forehead], the demarcation of vellus to terminal or intermediate hair in and adjacent to the midline of the anterior part of the head

generic: [L, genus, kind], of or pertaining to a substance, product, or drug that is not protected by trademark; identical in chemical composition but not necessarily equivalent in therapeutic effect

glycerin or glycerine: [Gk, glykeros, sweet], a sweet, colorless, oily fluid that is a pharmacologic grade of glycerol. Glycerin is used as a moistening agent for chapped skin, as an ingredient of suppositories for constipation and as a sweetening agent and vehicle for drug preparations.

Hamilton-Norwood: a graphic scale representing the extent of hair loss / recession of alopecia androgenetica in males

hirsutism: [L, hirsutus, hairy], excessive body or facial hair as a result of heredity, hormonal dysfunction, porphyria or medication. Also called hypertrichosis

hormone: [Gk, hormaein, to set in motion], a complex chemical substance produced in one part or organ of the body that initiates or regulates the activity of an organ or a group of cells in another part of the body

idiopathic: [Gk, idios, private, distinctive, peculiar + pathos, disease], without a known cause

intermediate hair: intermediate scalp hairs are approximately 1 cm in length. They lack the texture of terminal hair, but have much more thickness and body than vellus hair

in vitro: [L, in, within + vitreous, glassware], of a biologic reaction occurring in laboratory apparatus

in vivo: [L, in, within + vivo, alive], of a biologic reaction occurring in a living organism

keratin: [Gk, keras, horn], a fibrous, sulfur-containing protein that is the primary component of the epidermis, hair, nails and enamel of the teeth

ketoconazole: an antifungal medication that inhibits biosynthesis of ergosterols or other sterols

Ludwig staging: a graphic representation of the severity of alopecia androgenetica in women, originally published in 1977 in the British Journal of Dermatology

lunago: [L, down], the soft, fine hair that covers much of the fetus beginning in the fifth month and is usually shed before birth

minoxidil: a piperidinopyrimidine derivative vasodilator that possesses hair growth stimulant properties, possibly involving direct stimulation of hair follicle epithelial growth. The first FDA drug approved for the treatment of MPB

occiput: [L, occiput, atlas], the back part of the head

pharmacodynamics: [Gk, pharmakon, drug + dynamis, power], the study of how a drug acts on a living organism

pilosebaceous unit: [L, pilus, hair + sebum, fat], of or pertaining to a hair follicle and its oil gland

proprietary: [L, proprietas, a property], of or pertaining to a product, such as a drug or device, that is made for profit

propylene glycol: a colorless viscous liquid used as a solvent in the preparation of certain medications. It also inhibits the growth of fungi and microorganisms.

receptor site: [L, recipere, to receive +situs, location], a location on a cell surface where certain molecules, such as enzymes, neurotransmitters, or viruses, attach to interact with cellular components.

recession: [L, recedere, to retreat], a regression

Retin-A: the proprietary name for a preparation of retinoic acid, used in the treatment of acne and sun damage to the skin

retinoic acid (also tretinoin, isotretinoin or all-trans-retinoic acid): the cis-trans form of vitamin A. Retinoids act as a mild chemical peel on the skin and are very important to all epithelial structures

sebaceous: [L, sebum, sweat], fatty, oily or greasy, usually referring to the oil-secreting glands of the skin or to their secretions

sebum: [L, grease], the oily secretion of the sebaceous glands of the skin, composed of keratin, fat and cellular debris

steroid: [Gk, stereos,solid + eidos, form], any of a large number of hormonal substances with a similar basic chemical structure, produced mainly in the adrenal cortex and gonads

superoxide dismutase (SOD): chemicals that catalyzes the destruction of oxygen free radicals. It protects oxygen metabolizing cells against the harmful effects of superoxide free radicals.

telogen: [Gk, telos, end + genein, to produce], the resting phase of the hair growth cycle lasting approximately 100 days

temples or temporal areas: [L, tempus, temple], the lateral-frontal regions of the head

terminal hair: [L, terminus, boundary] of or pertaining to the thicker hair on the scalp that are medullated and have a growth phase of many years

testosterone: a naturally occurring androgenic hormone

vellus: the soft, fine hair covering all parts of the body except palms, soles and areas where other types of hair are normally found. True vellus hairs have no erector pili muscle, but have large sebaceous glands. Vellus scalp hairs achieve lengths less than 1 cm

vertex: [L, vertex, summit], the top of the head towards the posterior portion, including the area or areas at which the hair grows in a spiral pattern

Xandrox: the trademarked name of a 5% minoxidil / 5% azelaic acid solution by Regrowth, LLC for the treatment of alopecia androgenetica.

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