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Hair loss

Hair loss is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hair loss rather than just read about it. In short: Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved.

Hair loss — main illustration
Hair loss — illustration

Key takeaways

  • Hair loss belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Hair loss to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Hair loss from memory before moving on to harder problems.

Reference excerpt

Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarring is not usually present. Hair loss in some people causes psychological distress. Common types include male- or female-pattern hair loss, alopecia areata, and a thinning of hair known as telogen effluvium. The cause of male-pattern hair loss is a combination of genetics and male hormones; the cause of female pattern hair loss is unclear; the cause of alopecia areata is autoimmune; and the cause of telogen effluvium is typically a physically or psychologically stressful event. Telogen effluvium is very common following pregnancy. Less common causes of hair loss without inflammation or scarring include the pulling out of hair, certain medications including chemotherapy, HIV/AIDS, hypothyroidism, and malnutrition including vitamin B12 and iron deficiencies. Causes of hair loss that occurs with scarring or inflammation include fungal infection, lupus erythematosus, radiation therapy, and sarcoidosis. Diagnosis of hair loss is partly based on the areas affected. Treatment of pattern hair loss may simply involve accepting the condition, which can also include shaving one's head. Interventions that can be tried include the medications minoxidil (or finasteride) and hair transplant surgery. Alopecia areata may be treated by steroid injections in the affected area, but these need to be frequently repeated to be effective. Hair loss is a common experience. Pattern hair loss by age 50 affects about half of men and a quarter of women. About 2% of people develop alopecia areata at some point in time.

Terminology Baldness is the partial or complete lack of hair growth, and part of the wider topic of "hair thinning". The degree and pattern of baldness varies, but its most common cause is androgenic hair loss, alopecia androgenetica, or alopecia seborrheica, with the last term primarily used in Europe.

Hypotrichosis Hypotrichosis is a condition of abnormal hair patterns, predominantly loss or reduction. It occurs, most frequently, by the growth of vellus hair in areas of the body that normally produce terminal hair. Typically, the individual's hair growth is normal after birth, but shortly thereafter the hair is shed and replaced with sparse, abnormal hair growth. The new hair is typically fine, short and brittle, and may lack pigmentation. Baldness may be present by the time the subject is 25 years old.

Signs and symptoms

Symptoms of hair loss include hair loss in patches usually in circular patterns, dandruff, skin lesions, and scarring. Alopecia areata (mild – medium level) usually shows in unusual hair loss areas, e.g., eyebrows, backside of the head or above the ears, areas the male pattern baldness usually does not affect. In male-pattern hair loss, loss and thinning begin at the temples and the crown and hair either thins out or falls out. Female-pattern hair loss occurs at the frontal and parietal. People have between 100,000 and 150,000 hairs on their head. The number of strands normally lost in a day varies but on average is 100. In order to maintain a normal volume, hair must be replaced at the same rate at which it is lost. The first signs of hair thinning that people will often notice are more hairs than usual left in the hairbrush after brushing or in the basin after shampooing. Styling can also reveal areas of thinning, such as a wider parting or a thinning crown.

Skin conditions A substantially blemished face, back and limbs could point to cystic acne. The most severe form of the condition, cystic acne, arises from the same hormonal imbalances that cause hair loss and is associated with dihydrotestosterone production.

Psychological The psychology of hair thinning is a complex issue. Hair is considered an essential part of overall identity: especially for women, for whom it often represents femininity and attractiveness. Men typically associate a full head of hair with youth and vigor. People experiencing hair thinning often find themselves in a situation where their physical appearance is at odds with their own self-image and commonly worry that they appear older than they are or less attractive to others. Psychological problems due to baldness, if present, are typically most severe at the onset of symptoms. Two meta analyses on androgenetic alopecia revealed psychosocial distress levels to be moderate, on average, rather than severe and that balding men were no more likely to have depression or self esteem issues compared to non-balding men. Hair loss induced by cancer chemotherapy has been reported to cause changes in self-concept and body image. Body image does not return to the previous state after regrowth of hair for a majority of patients. In such cases, patients have difficulties expressing their feelings (alexithymia) and may be more prone to avoiding family conflicts. Family therapy can help families to cope with these psychological problems if they arise.

Causes Although not completely understood, hair loss can have many causes:

Pattern hair loss

Male pattern hair loss is believed to be due to a combination of genetics and the male hormone dihydrotestosterone. The cause in female pattern hair loss remains unclear.

Infection Dissecting cellulitis of the scalp Fungal infections (such as tinea capitis) Folliculitis from various causes Demodex folliculitis, caused by Demodex folliculorum, a microscopic mite that feeds on the sebum produced by the sebaceous glands, denies hair essential nutrients and can cause thinning. Demodex folliculorum is not present on every scalp and is more likely to live in an excessively oily scalp environment. Secondary syphilis

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. Some treatments used to cure mycotic infections can cause massive hair loss. Medications (side effects from drugs, including chemotherapy, anabolic steroids, and birth control pills)

… excerpt ends here. Continue reading the full article.

Illustrations

Hair loss illustration
Hair loss: A case of mid-frontal baldness: Andre Agassi
A case of mid-frontal baldness: Andre Agassi
Hair loss: Throughout his political career, Urho Kekkonen, the President of Finland, was well known for his baldness. He was last known to have had hair in about the 1920s.[11] This photo is of Kekkonen in 1959.
Throughout his political career, Urho Kekkonen, the President of Finland, was well known for his baldness. He was last known to have had hair in about the 1920s.[11] This photo is of Kekkonen in 1959.
Hair loss: Postpartum telogen effluvium
Postpartum telogen effluvium
Hair loss: General Douglas MacArthur with a comb over
General Douglas MacArthur with a comb over

Worked examples

Example 1 — a first encounter with Hair loss

Start with the simplest possible case. Write down what Hair loss claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hair loss before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hair loss ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hair loss

In research
Hair loss appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Hair loss in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Hair loss is common in secondary-school and first-year university syllabi. It links to neighbouring topics Conditions of the skin appendages, External signs of ageing, Hair diseases, so understanding it makes those chapters shorter.
In everyday life
Look for Hair loss outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Hair loss in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Hair loss means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Hair loss out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hair loss in simple terms?

Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved.

Why does Hair loss matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hair loss?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hair loss.

Tags

  • Conditions of the skin appendages
  • External signs of ageing
  • Hair diseases
  • Human hair
  • Radiation health effects

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