Many hormones in your body can inhibit hair growth. Sometimes having hormones out of balance that are otherwise benign in terms of affecting your hair can cause hair loss. Male and female hormones, along with some protein and thyroid hormones, can stall growth of your locks. Consult your doctor if you believe hormone imbalance is inhibiting your hair growth.
Parathyroid Hormone
Parathyroid hormone, or PTH, inhibits hair growth, according to Slobodan M. Jankovic and Snezana V. Jankovic, authors of an article published in Dermatology Online Journal. This protein hormone is released by your parathyroid gland, according to the National Institutes of Health. This hormone is your body's most important regulator for phosphorus and calcium levels in your body. The release of this hormone is controlled by the level of calcium in your blood. When you have low blood calcium levels, increased levels of the hormone are released. High blood calcium levels slow the hormone's release. The parathyroid is located next to the thyroid.
Estrogen
In certain circumstances, estrogen may inhibit hair growth. Topical application of an estrogen called 17-Beta oestradiol to skin inhibits hair growth and accelerates the catagen phase in the hair cycle, says Ulrike Blume-Peytavi in the book, "Hair Growth Disorders." Catagen is the phase in which hair growth stops before the resting phase in the hair growth cycle. 17-Beta oestradiol is the most potent estrogenic hormone in mammals and is produced in the placenta, ovary and testes. When your male and female hormones--known as androgens and estrogens--are out of balance, hair loss can occur, Family Doctor says.
Dihydrotestosterone
Dihydrotestosterone can inhibit hair growth in mice, says A. Naito, lead author for a study published in the British Journal of Dermatology. It's an androgen, or male hormone, that's required for sex development and is responsible for male characteristics during puberty--such as muscular growth and the deepening of the voice. Androgens cause regression of human hair follicles in the scalp area, says Naito. Dihydrotestosterone may inhibit hair growth by affecting androgen receptor signals in the body, according to Naito.
Thyroid
If your thyroid gland makes too much thyroid hormone, this may cause your hair to fall out, according to the National Institutes of Health. However, if your thyroid gland is underactive, meaning it makes too little of the hormone, your hair will become thin and brittle. In fact, human hair follicles are especially sensitive to thyroid hormone, says Philip W. Harvey, lead author for the book, "Endocrine and Hormonal Toxicology."
References
- "Dermatology Online Journal": The Control of Hair Growth; Slobodan M. Jankovic and Snezana V. Jankovic
- Medline Plus: PTH
- "Hair Growth and Disorders"; Ulrike Blume-Peytavi; 2008
- PubMed: "British Journal of Dermatology"; Dihydrotestosterone inhibits murine hair growth via the androgen receptor; A. Naito; 2008
- Family Doctor: Hair Loss and its Causes
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