The process of maintaining healthy and beautiful hair is complex. There is more to hair maintenance than one’s daily routine of hair products and supplements. Like the skin, the hair is also in tune with and may reflect a person’s health and well-being.
A simple complaint of baldness, hair thinning, or excess shedding warrants a thorough examination since it may be a manifestation of an underlying illness or condition like hormonal imbalance.
What does hormonal imbalance mean?
Hormones are messengers released by endocrine glands like the thyroid, gonads, adrenals, and pituitary glands. These are released into the bloodstream and act on different processes like one’s growth, development, and metabolism.
When different glands release either too much or too little of these hormones, imbalance occurs. This leads to untoward effects on various body parts, including the hair. Hormonal imbalance can outrightly impact the amount of hair loss (when the hair stops from growing) or shedding (when the hair falls off) .
What are the common sex hormones that affect hair loss and shedding?
These hormones are made in the different organs of the body. In pubescent males, testosterone is released from the testes, while in pubescent females, testosterone comes mostly from androstenedione made in the adrenal cortex and ovaries (see fig. 1).
Testosterone is also present in the hair follicles, where it can be converted to dihydrotestosterone (DHT) through the enzyme 5-alpha reductase . DHT causes hair miniaturization, where finer, lighter and short hair grow, which easily shed, as opposed to long, course, and darker hair. This condition is called androgenetic alopecia (male or female pattern baldness) .
Androgenetic alopecia is more common in males than in females. It presents in a specific pattern of hair loss. In males, it is initially evident as loss of the front hairline with a triangular pattern that later progresses to hair thinning and loss on the top of the scalp. The hair on the back and sides of the scalp is spared .
In females pattern hair loss, there is diffuse thinning of the center part of the scalp but the hairline is maintained. Both male and female patterned baldness-type hair loss can also happen in females if they have systemic conditions associated with the increased androgens like polycystic ovarian syndrome .
These hormones are made by the ovaries (see fig. 1). In contrast to androgens, estrogens lengthen the hair cycle phase, where there is continued hair growth, also called the anagen phase .
During pregnancy, high estrogen levels cause scalp hair to be longer and thicker. After giving birth, estrogen decrease leads to excessive hair shedding beyond the normal number of 50 to 100 strands per day. This condition is called acute telogen effluvium (TE), which lasts for 2-4 months. A gradual decrease of hair loss and regrowth of new hair is expected by 3 to 6 months .
Elevated progesterone levels send signals to the hypothalamus and pituitary glands to produce a gonadotrophin-releasing hormone (GnRH) and luteinizing hormones (LH), suppressing androgen synthesis by the gonads (see fig. 2).
Furthermore, high progesterone levels hamper the 5-alpha reductase enzyme decreasing the conversion of testosterone to DHT [2, 5]. Low levels of these androgens result in thicker, pigmented, and longer hair or non-miniaturized hair.
What is more, insulin resistance and hyperinsulinemia in menopause increase androgen secretion. Elevated androgen levels shorten the anagen phase and cause miniaturization of the scalp hair. Female pattern hair loss may also occur, affecting the scalp’s center areas [2, 5].
Thyroid gland hormones
The thyroid hormone thyroxine greatly influences the hair follicle. Studies have shown that thyroxine lengthens hair growth (anagen stage) and stimulates cells inside the hair to multiply further .
When the thyroid glands do not produce enough thyroid hormones (hypothyroidism), most of the hair will simultaneously and prematurely stop growing, and eventually shed, leading to hair thinning.
This hormone produced by the anterior pituitary gland is well-known for its role in milk-secreting (mammary) gland growth and milk production. Lately, its role in human hair growth has been investigated.
It was found that prolactin may inhibit hair shaft from growing longer by increasing androgens (testosterone and DHEAS) which also leads to hair loss , (see fig. 2).
The adrenal glands produce cortisol (stress hormone). It has a damaging effect on proteins that provide structural support to surrounding cells of tissues, including the hair (proteoglycans) .
These proteins are also vital in maintaining the normal growth of hair follicles. It is almost lost in the thin hair of patients with androgenetic alopecia. Damage to these proteins may increase hair shedding .
Low cortisol levels improve the size, proportion, and density of the hair by up to 25%. During acute stress, cortisol levels increase, which causes damage to hair proteoglycans. This affects hair follicles by hampering further growth leading to a sudden increase in hair shedding, a condition called acute telogen effluvium .
In acute TE, there’s a sudden onset of diffuse hair shedding, then thinning, which recovers after eliminating the triggering stress .
The pineal gland mainly secretes this hormone at night. Melatonin controls the sleep-wake cycle and is a strong anti-oxidant, which captures free radicals. It has a protective role and stops cell death (apoptosis) .
Moreover, it was found to block the DHT receptor sites (where DHT attaches) in the hair follicle. Melatonin is involved in enhancing hair color by increasing color-producing cells (melanocytes).
It is also found to make hair grow faster [2, 9]. People who have difficulty sleeping were found to have low melatonin levels, which may make some of their hair finer, lighter, shorter, and more prone to shedding.
A deeper understanding of hair biology and the body’s physiology is warranted in the proper diagnosis and management of various hair diseases. Besides hair growth stimulants, proper diagnosis is core in the treatment and management of hair loss or excessive shedding since imbalances in hormonal production are just one of the many reasons for this.
Like any other systemic diseases, early diagnosis and management, good health-seeking behavior, and a positive attitude are paramount in successful treatment response. Multispecialty management, involving physicians with different specialties such as dermatology, endocrinology, obstetrics and gynecology, and many others, is necessary to achieve an optimal treatment outcome.