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Thyroid hormones play a vital role in regulating metabolism, growth, and overall development—but their impact extends beyond internal systems. Proper thyroid function is also essential for the health and growth of hair and nails, with hair follicles being particularly sensitive to hormonal changes.
Recent research has shed light on the presence of thyroid hormone receptors—especially TRβ1—within hair follicles. These receptors are now known to influence the hair growth cycle, offering new insights into how hormonal imbalances can lead to hair thinning or loss.
Thyroid Hormones and Hair Follicles
Thyroid hormones play a key role in hair regeneration by directly influencing the activity of hair follicles. The thyroid gland produces two primary hormones—triiodothyronine (T3) and thyroxine (T4)—both of which are crucial for the growth, development, and regulation of hair follicles.
Hair follicles are tiny organs within the skin that contain specialized cells highly sensitive to changes in thyroid hormone levels. When these hormone levels fluctuate—either due to hypothyroidism or hyperthyroidism—the normal hair growth cycle can be disrupted, often leading to thinning hair, hair loss, or even baldness.
Understanding Thyroid Hormone Receptors in Hair Follicles
Billoni et al. (2000) examined thyroid hormone receptors in the hair follicle and sebaceous glands of the human body in the British Journal of Dermatology. The authors employed some immunohistochemistry methods and RT-PCR for reverse transcriptase polymerase chain in order to search for and estimate the thyroid hormone receptors.
The investigations showed that hair follicle TRβ1 is the primary receptor of the thyroid hormone. This is a significant finding because TRbeta1 mediates the effect of the thyroid hormones especially that of the active form triiodothyronine (T3). T3 binds with these receptors to modulate production of hormones which in turn influences the cellular processes responsible for hair follicle’s growth, maintenance and lifecycle.
The Impact of Thyroid Hormones on Hair Follicle Survival
In order to further analyze the impact of thyroid hormones on the representative follicular structures, hair follicles in human tissues were cultured in vitro as well as after treatment with T3. Their research proved that in vitro T3 even in physiological concentrations is effective in enhancing the survival of hair follicles (Billoni et al., 2000). This shows how important it is for people in general to maintain within normal limits their thyroid hormone concentration, since this can promote hair growth as well as prevent further loss of hair follicles.
There is sufficient evidence to support that abnormal thyroid hormone levels can exert a negative effect on hair. Most of hypothyroidism, this type of abnormality can be distinguished, often presenting the disorder of hair patterns which include hair damage accompanied by thinning and hair loss. Individuals suffering from hyperthyroidism also reported the limitation of hair growth or loss of hair due to the hyperactive thyroid emphasizing the treatment needed in order to have a healthy appearance of hair.
Imbalances of thyroid hormones are pertinent in hair thinning processes, whereby both hypothyroidism – underactive thyroid and hyperthyroidism – overactive thyroid, bring dysfunction to the hormone's synthesis, resulting in diffuse hair loss and global shredding of the hair density from the scalp.
Thyroid Hormone Imbalances and Hair Loss
Since hair growth progresses in cycles, the development of any imbalance of thyroid hormones can lead to hair loss. There are two extreme points of view: low levels of the thyroid hormones (hypothyroidism) and high levels (hyperthyroidism) and both can influence the hair follicles, resulting in hair loss.
Hair loss associated with hypothyroidism is characterized by droughts and cracks and hair is more likely to break while in hyperthyroidism, hair loss is associated with thin, fragile hair. Sometimes hair loss can also be related to thyroid hormone imbalances as in the case of autoimmune diseases like alopecia areata.
Diagnosing Thyroid-Related Hair Loss
Thyroid hair loss diagnosis is usually a multi-faceted approach consisting of a thorough history and clinical evaluation, in addition to laboratory investigations and thyroid disorders also warrant hormone assay. In order to identify disease processes that may cause hair loss other than thyroid disorder, a physician may conduct thyroid tests.
In other instances, a scalp evaluation may be necessary to determine the degree of hair loss as well as to look for other accompanying scalp pathologies. A few may need a biopsy to make a final diagnosis.
Treatment Options for Thyroid-Related Hair Loss
The type of hair loss treatment recommended for a person who has thyroid-affect hair loss primarily involves assessing the root cause of the condition. Where there is evidence of hair loss due to excessive or less than normal thyroid hormone, corrective measures will be centered around the administration of drugs that will restore the levels of thyroid hormones.
Thyroid hormone replacement therapy may also be needed to restore the levels to normal thyroid hormone levels. Currently, hair loss treatment options like medications include minoxidil or finasteride which are helpful in stimulating hair growth. Other measures such as diet change, stress management, and using hair-friendly products can be beneficial for less hair loss and good hair growth too.
Clinical Implications and Future Research
The finding that the expression of TRβ1 in hair follicles is constrained in TRβ1 −/− mice for the first time has important clinical reasons. It clarifies why depending on the thyroid disorder one has, for example hypothyroidism or hyperthyroidism, the conditions of the hair will be affected.
It has been shown that hair loss is connected to autoimmune thyroid diseases, such as alopecia areata. Prevalence of an autoimmune disease in individuals has an inverse relationship with the risk of developing autoimmune diseases and alopecia, which might occur with significant hair loss.
Hair loss and environmental fatigue are common features of a person having a thyroid disorder like hypothyroidism, which is characterized by heavy hair loss and fatigue. Various types of adverse thyroid hormones levels, that is over or under active thyroid, causes hair distribution to be such that hair growth is halted all over the body and hair shedding occurs across the body parts even among the scalp.
The findings also suggest that targeted hormone therapies could be developed for hair loss as a consequence of thyroid imbalance through the hormone receptor activity. In patients suffering from hair loss related to thyroid disorders, it may be critical to manage their thyroid conditions in order to preserve or promote hair regrowth.
The work of Billoni et al. 2000 provides some valuable information, however, more effort needs to be invested in establishing exactly how T3 and T4 hormones affect hair follicle growth and cycling. Further, it would also be fruitful to investigate how thyroid hormones may interact with different pathways involved in hair growth for better understanding of hair loss conditions.
Conclusion
Thyroid hormones have a systemic and multi directional action, encompassing metabolism, growth, and even hair follicles health. An underactive thyroid can lead to hair loss, making it crucial to manage thyroid hormone levels. The stimulation of hair follicles TRβ1 and the positive actions of T3 in follicle survival indicate that there is a linkage between thyroid and hair structures.
In cases of hair loss especially those associated with thyroid disease it would be prudent to consider regulating the thyroid hormones in order to achieve hair restoration and retention.
References
Billoni, N., Buan, B., Gautier, B., Gaillard, O., Mahé, Y. F., & Bernard, B. A. (2000). Thyroid hormone receptor beta1 is expressed in the human hair follicle. British Journal of Dermatology, 142(4), 645-652. https://doi.org/10.1046/j.1365-2133.2000.03408.x.
