Hair Loss

Hair loss, also known as alopecia or baldness, refers to a loss of hair from the head or body. Baldness can refer to general hair loss or male pattern hair loss.

Hair loss and hypotrichosis have many causes including and rogenetic alopecia, fungal infection, trauma, radiotherapy, chemotherapy, nutritional deficiencies, and autoimmune diseases. Hair loss severity occurs across a spectrum with extreme examples including alopecia totalis and alopecia universalis .

Hair Loss Causes

Male pattern baldness

More than 95% of hair loss in men is male pattern. MPB is characterized by hair receding from the lateral sides of the forehead. Both become more pronounced until they eventually meet, leaving a horseshoe-shaped ring of hair around the back of the head.

The incidence of pattern baldness varies from population to population and is based on genetic background. Environmental factors do not seem to affect this type of baldness greatly. One large scale study in Maryborough, Victoria, Australia showed the prevalence of mid-frontal baldness increases with age and affects 73.5 percent of men and 57 percent of women aged 80 and over. A rough rule of thumb is that the incidence of baldness in males corresponds roughly to chronological age. For example, according to Medem Medical Library's website, MPB affects roughly 40 million men in the United States. Approximately one in four men will have noticeable hair loss by age 30, and this figure increases to two in three men by age 60. In rare cases, MPB can begin as early as age 12.

The genetics of MPB are not yet fully understood. Most likely there are multiple genes that contribute towards MPB, the most important of which appears to be the Androgen Receptor gene, located on the X chromosome. It was previously believed that baldness was inherited from the maternal grandfather. While there is some basis for this belief, it is now known that both parents contribute to their offspring's likelihood of hair loss. Most likely, inheritance involves many genes with variable penetrance.

The trigger for this type of baldness is dihydrotestosterone, a more potent form of testosterone often referred to by its acronym DHT. DHT is an androgenic hormone, body- and facial-hair growth promoter that can adversely affect the prostate as well as the hair located on the head. The mechanism by which DHT accomplishes this is not yet fully understood. In genetically prone scalps, DHT initiates a process of follicular miniaturization, in which the hair follicle begins to deteriorate. As a consequence, the hair’s growth phase is shortened, and young, unpigmented vellus hair is prevented from growing and maturing into the deeply rooted and pigmented terminal hair that makes up 90 percent of the hair on the head.[12] In time, hair becomes thinner, and its overall volume is reduced so that it resembles fragile vellus hair or "peach fuzz" until, finally, the follicle goes dormant and ceases producing hair completely.

Drugs

Temporary or permanent hair loss can be caused by several medications, including those for blood pressure problems, diabetes, heart disease and cholesterol. Any that affect the body’s hormone balance can have a pronounced effect: these include the contraceptive pill, hormone replacement therapy, steroids and acne medications.

Trauma

Traction alopecia is most commonly found in people with ponytails or cornrows who pull on their hair with excessive force. In addition, rigorous brushing and heat styling, rough scalp massage can damage the cuticle, the hard outer casing of the hair. This causes individual strands to become weak and break off, reducing overall hair volume.

Trichotillomania is the loss of hair caused by compulsive pulling and bending of the hairs. Onset of this disorder tends to begin around the onset of puberty and usually continues through adulthood. Due to the constant extraction of the hair roots, permanent hair loss can occur.

Traumas such as childbirth, major surgery, poisoning, and severe stress may cause a hair loss condition known as telogen effluvium, in which a large number of hairs enter the resting phase at the same time, causing shedding and subsequent thinning. The condition also presents as a side effect of chemotherapy – while targeting dividing cancer cells, this treatment also affects hair’s growth phase with the result that almost 90% of hairs fall out soon after chemotherapy starts.

Radiation to the scalp, as when radiotherapy is applied to the head for the treatment of certain cancers there, can cause baldness of the irradiated areas.

Content Source from https://en.wikipedia.org/wiki/Hair_loss