Study of the Thyroid Profile of Patients with Alopecia

Abstract

Thyroid hormones are required for the physiological growth and maintenance of hair follicles. We aim to study the thyroid profile of patients with alopecia. This is a narrative review. PubMed literature was searched from 2013 to 2022. We followed different types of alopecia: alopecia areata (AA), androgenic alopecia in males and females, telogen effluvium (TE), frontal fibrosing alopecia (FFA), lichen planopilaris, and alopecia neoplastica (AN). AA shares a common autoimmune background with autoimmune thyroid diseases, either sporadic or belonging to autoimmune polyglandular syndromes. Some data suggested that AA is more severe if thyroid anomalies are confirmed, including subclinical dysfunction or positive antithyroid antibodies with normal hormone values. However, routine thyroid screening for patients with AA, if the patients are asymptomatic from a thyroid point of view and they have negative personal and family history of autoimmunity, remains controversial. TE, apart from the autoimmune type, associates thyroid anomalies of a hormonal assay (between 5.7% and 17%). FFA, mostly a postmenopausal entity (however, not exclusive), associates a higher prevalence of thyroid conditions (up to 50%) than the general population. However, these might have an age-dependent pattern, thus the association may be incidental since there are a limited number of studies. Overall, alopecia remains a very challenging condition for patients and physicians; a multidisciplinary team is required to improve the outcome and quality of life. The common autoimmune background is suggestive of some types of alopecia and thyroid disorders, yet, the underlying mechanisms are still a matter of debate. AA, TE, FFA, LPP, and, potentially, female pattern hair loss have been found to be connected with thyroid entities, thus a state of awareness from a dual perspective, of trichology and endocrinology, is helpful.

The Hormonal Background of Hair Loss in Non-Scarring Alopecias

“…On the other hand, regulatory T cells are involved in both AA and thyroid condition progression. In line with this, some studies demonstrate a higher likelihood of AA in patients suffering from autoimmune hyperthyroidism or hypothyroidism as compared with healthy controls [ 100 , 102 ].…”

“…For example, a study on 1232 men and women for 25 months identified 14.29% ( n = 176) of them with MPA. The prevalence of thyroid dysfunctions in the MPA subgroup differed with age as follows: 6.3% in patients below 20 years old, 17% in persons aged between 21 and 40 years, and 50% in individuals older than 40 years [ 102 ].…”

“…Unlike alopecia areata, telogen effluvium is linked to the thyroid hormones’ bloodstream levels and not to autoimmune conditions [ 102 ]. As T3 and T4 affect the follicles directly and make them sensitive during anagen, their low blood levels in hypothyroidism may lead to hair loss with prolonged shedding and also changes in hair texture [ 100 ].…”

Is thyroid dysfunction a common cause of telogen effluvium?: A retrospective study

“…The prolonged telogen phase eventually results in excessive shedding of resting hair, resulting in the typical hair loss seen in TE. [18] Table 1 Summary of our result. 1 Showed that the hypothyroidism group had significantly higher mean SALT scores than both the euthyroid and hyperthyroidism groups (P < .001).…”

Melatonin’s effect on hair follicles in a goat (Capra hircus) animal model

“…Alopecia (hair loss) due to endocrine disorders has always plagued humans ( 1 , 2 ). Animal models for studying hair follicles in humans are usually rats ( 3 ), mice ( 4 ), guinea pigs ( 5 ), rabbits ( 6 ), and dogs ( 7 ).…”