A small butterfly-shaped organ in the front of our neck is none other than the thyroid gland. This small and precious thyroid gland secretes thyroid hormone (T3, T4), which regulates the body's metabolic rate. It functions much like a throttle controlling the output of an engine. These hormones are involved in almost every function of our body, including body temperature maintenance, energy production, and cell growth and regeneration. Hair growth is no exception. Thyroid hormone plays a key role in promoting the division and growth of hair follicle cells and regulating each phase of the hair growth cycle.
What happens if a disorder develops in thyroid function? The most common is hypothyroidism. When thyroid hormone secretion decreases, the body's metabolic rate slows down overall. The hair growth cycle also slows, and hair follicles either linger longer in the telogen phase or enter the telogen phase prematurely in increasing numbers. As a result, hair easily becomes thin, dry, and brittle, and one can even experience diffuse alopecia where hair volume diminishes across the entire head. A noticeable reduction in overall volume occurs as hair falls out weakly and new hair fails to grow well. Along with hair changes, dry skin, weight gain, chronic fatigue, and feeling cold easily may also be present.
Conversely, hyperthyroidism can also be a cause of alopecia. When hormone is excessively secreted, metabolism becomes too fast, abnormally shortening the hair growth cycle. In this case, hair can become extremely fine, weak, and brittle, and in severe cases, diffuse alopecia may occur. At times, the thyroid disease itself is a type of autoimmune disease, such as Hashimoto's thyroiditis or Graves' disease. Because such autoimmune diseases can induce or worsen other types of autoimmune alopecia, such as alopecia areata, even more careful attention is required.
An imbalance in thyroid hormone can also affect the protein structure of hair, making it weak and easily breakable. Therefore, if hair suddenly falls out noticeably or becomes unusually dry and brittle, scalp care alone might not resolve it. It is important to find the accurate cause through a blood test to check thyroid hormone levels (thyroid-stimulating hormone, free T3, free thyroxine) and, if necessary, even a thyroid antibody test. The health of the kidney and blood, which Donguibogam calls the root of the body, is closely connected in modern medicine to the harmonious function of endocrine organs like the thyroid gland. Healthy hair begins with a healthy body.
