biology

Pattern hair loss

Pattern 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 Pattern hair loss rather than just read about it. In short: Pattern hair loss, also known as androgenetic alopecia, is a hair loss condition that primarily affects the top and front of the scalp. In male-pattern hair loss, the hair loss typically presents itself as either a receding front hairline, loss of hair on the crown and vertex of the scalp, or a combination of both.

Key takeaways

Pattern 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 Pattern hair loss to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pattern hair loss from memory before moving on to harder problems.

Reference excerpt

Pattern hair loss, also known as androgenetic alopecia, is a hair loss condition that primarily affects the top and front of the scalp. In male-pattern hair loss, the hair loss typically presents itself as either a receding front hairline, loss of hair on the crown and vertex of the scalp, or a combination of both. Female-pattern hair loss typically presents as a diffuse thinning of the hair across the entire scalp. The condition is caused by a combination of male sex hormones and genetic factors. Some research has found evidence for the role of oxidative stress in hair loss, the microbiome of the scalp, genetics, and circulating androgens; particularly dihydrotestosterone. Men with early onset androgenic alopecia (before the age of 35) have been deemed the male phenotypic equivalent for polyendocrine metabolic ovarian syndrome. The cause of female pattern hair loss remains unclear; androgenetic alopecia for women is associated with an increased risk of polyendocrine metabolic ovarian syndrome. Management of hair loss may include styling the remaining hair in a creative manner to make hair loss less apparent or shaving one's head to improve the aesthetic aspect of the condition. Otherwise, common medical treatments include platelet-rich plasma, low-level laser therapy, minoxidil, finasteride, dutasteride, or hair transplant surgery. Use of finasteride and dutasteride in women is not well-studied and may result in birth defects if taken during pregnancy. By the age of 50, pattern hair loss affects about half of males and a quarter of females. It is the most common cause of hair loss. Both males aged 40–91 and younger male patients of early onset androgenetic alopecia (before the age of 35) had a higher likelihood of metabolic syndrome (MetS) and insulin resistance. In both older and younger populations of men who had early onset androgenic alopecia, metabolic syndrome has been found to occur approximately four times as frequently as in a demographically similar population without androgenic alopecia, which is a clinically significant difference. Abdominal obesity, hypertension, and lowered high-density lipoprotein were also significantly higher for younger groups.

Signs and symptoms

Pattern hair loss is classified as a form of noncicatricial alopecia, i.e. a sort of non-inflammatory non-scarring hair loss. Male-pattern hair loss begins above the temples and at the vertex (calvaria) of the scalp. As it progresses, a rim of hair at the sides and rear of the head remains. This has been referred to as a "Hippocratic wreath" and rarely progresses to complete baldness. Female-pattern hair loss more often causes diffuse thinning without hairline recession; similar to its male counterpart, female androgenic alopecia rarely leads to total hair loss. The Ludwig scale grades severity of female-pattern hair loss. These include Grades 1, 2, 3 of balding in women based on their scalp showing in the front due to thinning of hair. In most cases, receding hairline is the first starting point; the hairline starts moving backwards from the front of the head and the sides.

Causes The cause of pattern hair loss is not yet fully understood. It appears to be the result of genetic changes that make the activity of hair follicles on the scalp become sensitive to the presence of androgenic hormones, cholesterol, and proteins such as insulin-like growth factor.

Hormones and genes KRT37 is the only keratin that is regulated by androgens. This sensitivity to androgens was acquired by Homo sapiens and is not shared with their great ape cousins. Although Winter et al. found that KRT37 is expressed in all the hair follicles of chimpanzees, it was not detected in the head hair of modern humans. As androgens are known to grow hair on the body but decrease it on the scalp, this lack of scalp KRT37 may help explain the paradoxical nature of Androgenic alopecia as well as the fact that head hair anagen cycles are extremely long. Although it is generally accepted that male pattern baldness follows a pattern of autosomal dominant inheritance, more recent research has shown that approximately 80% of bald men have bald fathers. This is greater than would be expected if pattern balding were a purely autosomal trait, and may suggest that there is an important paternal route of inheritance, either through a Y-chromosome gene or a paternal imprinting effect.

… excerpt ends here. Continue reading the full article.

Illustrations

Pattern hair loss: Androgens can interact with the Wnt signalling pathway to cause hair loss — Androgens can interact with the Wnt signalling pathway to cause hair loss

Worked examples

Example 1 — a first encounter with Pattern hair loss

Start with the simplest possible case. Write down what Pattern 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 Pattern 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 Pattern 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 Pattern hair loss

In research: Pattern 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 Pattern 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: Pattern hair loss is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ailments of unknown cause, Androgens, Conditions of the skin appendages, so understanding it makes those chapters shorter.
In everyday life: Look for Pattern 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 Pattern hair loss in 20 minutes

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

Frequently asked questions

What is Pattern hair loss in simple terms?

Why does Pattern 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 Pattern 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 Pattern hair loss.