Hair thinning

Thinning hair refers to minor to moderate hair loss. Unlike widespread hair loss, thinning hair doesn’t necessarily cause baldness. It does, however, give the appearance of thinner spots of hair on the head. Thinning hair may be caused by lifestyle habits, genetics, or both. Certain medical conditions may also lead to thinning hair.

Most elderly people experience hair thinning as one expression of aging. As people get older, their hair may start to lose volume and thickness, which can be linked with diet, nutrient deficiencies, or hereditary hair loss. Although this is very normal and not linked with overall health concerns, it can affect people's mental health and self-esteem.

Telogen effluvium is a condition that is characterized by a period of temporary hair thinning or an increase in hair shedding, which might eventually lead to hair loss. It occurs more often in women and is usually triggered by a disturbance to the hair cycle. Some of the causes are: severe stress, poor diet, sudden weight loss, pregnancy and childbirth, menopause, certain medication or recreational drugs, underlying health conditions, surgery, and metal toxicity. 

According to the American Osteopathic College of Dermatology, 

It is normal to lose up to about 100 hairs a day; this is the result of the normal hair growth cycle. Hairs will grow for a few years, then rest for a few months, shed, and regrow. Telogen is the name for the resting stage of the hair growth cycle. A telogen effluvium is when some stress causes hair roots to be pushed prematurely into the resting state. Telogen effluvium can be acute or chronic.

If there is some "shock to the system", as many as 70% of the scalp hairs are then shed in large numbers about 2 months after the "shock". This sudden increase in hair loss is called acute telogen effluvium. This is a different problem than gradual genetic hair thinning. However, this can be seen in the less common chronic telogen effluvium, only after a significant amount of hair has already been lost.

No treatment is needed for most cases of telogen effluvium, as with this type of hair loss, hair falling out is a sign of hair regrowth. As the new hair first comes up through the scalp and pushes out the dead hair a fine fringe of new hair is often evident along the forehead hairline.

Chronic telogen effluvium is recently recognized and not uncommon. It often occurs in women who previously had very thick hair in their teens and twenties and still have an apparently normal head of hair to a casual observer. It affects the entire scalp with no obvious cause apparent. It usually affects women of 30 to 60 years of age, starts suddenly and has a tendency to fluctuate for a period of years. The degree of shedding is usually severe in the early stages and the hair may come out in handfuls. It does not cause complete baldness and does appear to be self-limiting in the long run.

Hair thinning is very common in both males and females regardless of their ethnicity. It is sometimes confused with alopecia, which is widespread hair loss. While thinning hair may eventually lead to hair loss, these two entities aren’t necessarily the same thing.