The different phases may last for varying periods of times from several years in anagen, to a few months in telogen or several weeks in anagen. Fortunately not all hair follicles are in the same phase at the same time. So the majority of the follicles will be in anagen phase, while a smaller amount will be in the catagen phase and a few follicles will be in the telogen phase. This ensures that there is always some hair present even when the follicle is not active and the hair is not growing.
No one wants to lose their hair, but for a woman it is particularly distressing. While men can look perfectly presentable — even sexy — with their exposed scalp, no such options exist for the 30 million American women who grapple with thinning tresses. Dr. Maria Colavincenzo, a dermatologist at Northwestern University Feinberg School of Medicine, has a practice that specializes in preserving those precious strands — especially in cases of androgenetic alopecia, a hereditary condition that causes hair loss, mainly on the top and crown of the scalp. Without an appointment, she answered some of our questions:
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In men, finasteride (originally marketed as Proscar) is approved for hair loss associated with androgens. In one study, 62% of women also taking oral contraceptives containing the synthetic progestin drospirenone reported improvement. So it may be effective for female hair loss in the setting of increased androgen. But studies are limited and it is harmful to the male fetus so should not be used by women thinking about becoming pregnant or who are pregnant.
Another reason that you have thinning eyebrows might be low thyroid (which is called hypothyroidism. The thyroid gland controls the rate of use of energy sources, protein synthesis by producing thyroid hormones. I the thyroid gland does not produce enough hormones, you might feel tired, freeze in the cold, gain weight or lose your hair. The most common cause of hypothyroidism is iodine deficiency.
Women using oestrogen supplementation or taking birth control pills will also experience hair loss when they cease supplying their body with extra oestrogen. These forms of hair loss may be temporary but this, however, does not mean that there is no link between oestrogen and permanent hair loss. Scientists have noted up to 30 hormones that could play a role in female pattern hair loss – the genetic kind of hair loss – and oestrogen, whilst poorly explored, may be one of them. It’s alright if the excess hairs are the ones that are lost but when normal hair falls out, there’s a problem.
After giving birth, reaching menopause years or experiencing other hormonal imbalances, it’s not uncommon for women to start losing hair. And while hair loss is a normal process (the American Academy of Dermatology estimates the average person sheds about 50-100 hairs a day), it’s also something that can be remedied by addressing underlying health and hormonal problems.
Hair loss may also occur due to dieting. Franchised diet programs which are designed or administered under the direction of a physician with prescribed meals, dietary supplements and vitamin ingestion have become popular. Sometimes the client is told that vitamins are a necessary part of the program to prevent hair loss associated with dieting. From a dermatologists’s standpoint, however, the vitamins cannot prevent hair loss associated with rapid, significant weight loss. Furthermore, many of these supplements are high in vitamin A which can magnify the hair loss.
Insulin regulation is also a big factor in hair health, as an imbalance can lead to various hormonal effects. Insulin helps to regulate blood sugar levels, which effects fat storage and hormone balance. Fat storage and hormone balance play a role in hair growth because fat storages will secrete excess estrogen in the body, and can desensitize hormone signals.
Estrogen and combined oral contraceptive (COC) drugs with estrogen or progestogen have been reported as effective, but data are limited (Adenuga et al., 2012, Raudrant and Rabe, 2003, Scheinfeld, 2008). They are thought to function through several mechanisms. Both components of COC drugs increase the levels of sex-hormone-binding globulin (Schindler, 2013). They also send negative feedback signals that suppress the hypothalamic secretion of gonadotropin and releases the hormone and pituitary secretion of the luteinizing and follicle-stimulating hormones, which results in a decreased androgen production (Gilman et al., 1990, Varothai and Bergfeld, 2014). These actions decrease androgen secretion from the ovary and the quantity of free, biologically active androgens, which reduces their effects on the hair follicles (Schindler, 2013). Our practice when prescribing COC drugs is a combination of ethinyl estradiol 20 mcg plus drospirenone 3 mg. Drospirenone is an analogue of spironolactone. This treatment combination is approved by the FDA for the treatment of acne but not alopecia.
The majority of women with androgenic alopecia have diffuse thinning on all areas of the scalp. Men on the other hand, rarely have diffuse thinning but instead have more distinct patterns of baldness. Some women may have a combination of two pattern types. Androgenic alopecia in women is due to the action of androgens, male hormones that are typically present in only small amounts. Androgenic alopecia can be caused by a variety of factors tied to the actions of hormones, including, ovarian cysts, the taking of high androgen index birth control pills, pregnancy, and menopause. Just like in men the hormone DHT appears to be at least partially to blame for the miniaturization of hair follicles in women suffering with female pattern baldness. Heredity plays a major factor in the disease.
Hansen's disease, also known as leprosy, is an infection of the skin and nerves caused by the bacterium Mycobacterium leprae. The disease often affects the skin of the eyebrow region, leading to loss of sensation and permanent loss of the eyebrow hairs. There are numerous other rare and uncommon causes of eyebrow hair loss, including vitamin A toxicity, nutritional disorders and other dermatological disorders. If you experience loss of eyebrow hair, see your doctor to evaluate the cause and to discuss a treatment plan.