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Evaluation of thyroid function status in patients with alopecia areata

Alopecia areata (AA) is a heterogeneous variant of alopecia characterized by patchy and scarless loss of hair secondary to the destruction of anagen phase hair follicles in different regions of the body and could involve the nails. It commonly presents in the scalp region with no race, sex or age predilection. However, several authors had documented that the condition presents mainly among the younger age groups with a reported global population prevalence rate of 1%. The true incidence and prevalence rates of alopecia areata in Africa is poorly-documented and ill-defined, however, in Nigeria, recent reports from the north and south-west part of the country had documented a prevalence rate between 1– 1.2% of the disorder among the population.


INTRODUCTION
Alopecia areata (AA) is a heterogeneous variant of alopecia characterized by patchy and scarless loss of hair secondary to the destruction of anagen phase hair follicles in different regions of the body and could involve the nails. 1,2 It commonly presents in the scalp region with no race, sex or age predilection. 3 However, several authors had documented that the condition presents mainly among the younger age groups with a reported global population prevalence rate of 1%. 3,4 The true incidence and prevalence rates of alopecia areata in Africa is poorly-documented and ill-defined, however, in Nigeria, recent reports from the north and south-west part of the country had documented a prevalence rate between 1-1.2% of the disorder among the population. 5,6 Decades-long after AA was first described and documented in the literature, its etiopathogenesis has remained elusive in the medical parlance. 7,8 However, different postulations and theories have been put forward to elucidate the exact pathway of its evolution. The first theory put forward was the viral, fungal, and bacterial infection theory, followed by the genetic theory, and finally the environmental theory. 9,10 These theories had all been adduced as triggers of AA evolution in humans by various authors. [10][11][12] However, the most accepted and plausible of these theories in AA evolution and etiopathogenesis is based on that of autoimmunity which posits that AA is an autoimmune disease directed against putative autoantigen of anagen phase hair follicles. 11 The autoimmunity theory of AA is based on evidencebased findings of infiltrative inflammatory CD4+ and CD8+ T cells in biopsy specimen of affected hair follicles of AA patients, accompanied by hair follicle-specific autoantibodies within these AA lesions and in the peripheral blood of patients with AA, and the response of treatment of AA to immunosuppressive agents. [11][12][13][14][15] Most importantly, AA is associated with varied other autoimmune disorders including vitiligo, rheumatoid arthritis, pernicious anemia, and thyroid function abnormalities. 11,16 Thyroid function abnormalities secondary to autoimmune mechanism are the most prominent of these disorders documented and reported among AA patients in the literature. [17][18][19][20][21][22] However, these thyroid function abnormalities have mostly been observed in the western population with a paucity of clinical data in Nigeria. Therefore, this study was conducted in essence to investigate the status of thyroid function among indigenous Nigerian patients with AA.

Objectives
 To determine the pattern of thyroid function abnormalities among patients with AA  To determine the sex distribution of thyroid function abnormalities among patients with AA.  To compare the results of this study with the literature. Data of 113 of these records met the inclusion criteria and were recruited for the study. Eight of these records were excluded because five had incomplete data and three were on treatment for already diagnosed thyroid disorders.

This
In Table 1     In Table 2, the majority (61.9%) of the study cohorts were in the age group 20 to 40 years while the least (1.9%) were above 60 years of age.
In Table 3, thyroid function abnormalities were observed in 27.3% of the study cohorts with a female preponderance (18 female versus 13 males).
In Table 4, the most prevalent thyroid function abnormality observed in both sexes is hypothyroidism (16.8% subclinical and 4.4% primary) and the female predominated in both cases of hypothyroidism. Secondary disorders of thyroid function were not observed among the study cohorts.

DISCUSSION
Alopecia areata (AA) is a heterogeneous variant of alopecia characterized by the patchy non-scaring loss of anagen phase hair follicles which sometimes involves the nails in very severe variants. 1 It has an unpredictable clinical course with no sex, age, or racial predilection. 1,2 In terms of sex characteristics of AA patients, some authors had suggested a more male preponderance while others found no difference. 11 In this study, we found no statistical difference in the sex distribution among our study cohorts, however, females were more than the males. The higher female number observed could be related to the increased concern of women for their physical appearance than the men.
The condition can occur at any age but seem to be more prevalent among the younger age groups. 23 The youngest patient reported in the literature was four months old while the oldest was in the late seventies. 24 Several authors have documented several peak age of onset of AA. While others have reported less than twenty years of age as the peak, others have reported between twenty and forty years. 24 However, the generality of these reports have reported on the age group twenty to forty years as the peak age of onset of AA. 25 In this study, the majority (61.9%) of the study cohorts were in the age range twenty to forty years which is in accord with the generality of the reports in the literature.
The etiopathogenesis of alopecia areata has remained an enigma several decades after it was first described in the literature. 7,8 However, several theories had been adduced to its evolution and etiopathogenesis in humans in recent years among them viral and fungal infections, genetics, environmental, and autoimmunity. 11 Among these several theories, the theory of autoimmunity seems the most plausible theory evidenced by the local inflammatory infiltrates of T cells in AA lesions, the specific autoantibodies against anagen phase hair follicles in alopecia areata lesions and in the peripheral blood of patients with AA, the response of alopecia areata to immunosuppressive agents, and the concomitant manifestation of other autoimmune diseases in alopecia areata. [11][12][13][14][15] Among the various other disorders secondary to this autoimmune mechanism associated with alopecia areata, thyroid function abnormalities are the most reported among these patients with alopecia areata. 17 [17][18][19][20] In this study, the prevalence of thyroid function abnormalities observed among our study cohorts was 27.3%, which is higher than the reports from these previous studies and suggest an increased prevalence of thyroid function abnormalities among our study cohorts.
The most common thyroid function abnormality noted among alopecia areata patients in the literature is hypothyroidism. Bakery et al had reported a high rate of subclinical hypothyroidism as the most common thyroid functional abnormality among Egyptian patients with alopecia areata. In a clinical study conducted among alopecia areata subjects by Thomas and Kadyan, hypothyroidism was reported as the most prevalent of thyroid function abnormalities. While Lyakhovitsky et al also noted a similar pattern of hypothyroidism in their own study. 21,22 These reports are all in accord with the findings of this study where we noted that majority of the alopecia areata patients presented with hypothyroidism with subclinical hypothyroidism predominating.

CONCLUSION
The finding of this study suggest an association of alopecia areata with thyroid function abnormalities and supports the numerous reports of high prevalence of thyroid disorders in patients with alopecia areata. Therefore, patients who present with alopecia areata should be screened for thyroid function abnormalities irrespective of clinical status.