Goitrogenic and Antithyroid Potential of Green Tea of Indian Origin

Abstract

Polyphenolic flavonoids, specially catechins are major constituents of tea. Antithyroidal and goitrogenic effect of flavonoids have been reported however such effects of green tea on thyroid physiology has not been explored earlier. Green tea is derived from the tea leaves of Camellia sinensis and widely consumed globally. The green tea extracts(GTE) at different concentrations (1.25g% a” 5 cups of tea/ day; 2.5g% a” 10 cups of tea/ day and 5.0g% a” 20 cups of tea/ day) were orally fed to male rats for 30 days. Similarly, pure catechin was administered orally to male albino rats for 30 days at doses of 25, 50 and 100 mg/kg body weight that are equivalent to above doses of green tea extract in terms of its total catechin content and the morphological and functional changes of the thyroid have been investigated. The overall results reveal that oral administration of green tea extract at 2.5g% and 5.0g% concentrations for 30 days changed the morphology and histology resembling hypertrophy of thyroid follicles with differential colloid sizes as found in hypothyroid due to environment influences associated with significant inhibited activities of thyroid peroxidase(TPO) and 5’ monodeiodinase (5’ DI1) with elevated Na+,K+ ATPase and concomitant decrease in serum thyroxine (T4), triiodothyronine (T3) and increase in serum thyrotropin (TSH) levels developing a state of absolute biochemical hypothyroidism. All these suggest that catechin present in green tea has the antithyroidal as well as goitrogenic potential and its regular consumption at relatively high doses pose a threat to the functioning of thyroid. DOI: http://dx.doi.org/10.3329/jbsp.v9i2.22807 Bangladesh Soc Physiol. 2014, December; 9(2): 105-116

Evaluation of the Activity of Some Plants Extracts on Thyroid Gland Regulation in Female Albino Rats

“…The highest increase in TSH level was by 10% for 1.25mg/kg treatment, while the maximum reductions of T3 and T4 levels were by 20 and 3%, respectively, for 1.25 mg/kg of the same treatment, compared with the control. These findings are in agreement with a previous study [14] which found that catechin present in green tea has an antithyroidal potential and reduced the levels of triiodothyronin and thyroxine, while the level of TSH was increased. These results are related to the chemical composiition of C. sinensis with the presence of wide range of phytochemicals that are digested, absorbed and metabolized by the body.…”

“…These were surrounded by a thick layer of adipose connective tissue (Figure-1f). These results are in agreement with Chandra et al, (2014) who found that the thyroid appeared normal both grossly and microscopically using a mild dose (1.25 mg/kg), but the changes appeared with a moderate dose of 2.5 mg/kg daily for 30 days. These changes were represented by diffused hypertrophy and/or hyperplasia of the thyroid follicular epithelial cells, with less amount of colloidal material and irregularly shaped follicles that have decreased luminal spaces with tall cuboidal follicular epithelium.…”

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“…Moreover, the commercially available catechins have shown pronounced effect inducing hypothyroidism which validates that the effect of GTE may be due to antithyroidal or goitrogenic effect of catechins present in tea. All these suggest that catechin present in green tea has the antithyroidal as well as goitrogenic potential and its regular consumption at relatively high doses pose a threat to the functioning of thyroid 84 .…”

The Effects of Green Tea on the Body Weight and Histoarchitecture of the Testis of Adult Male Sprague dawley Rats

“…[14,15] It has been reported that there was a decrease in plasma testosterone level by green tea epigallocatechin-gallate (EGCG). Goitrogenic/anti-thyroidal effect of GTE, in relatively high doses has been reported in both in-vivo and in-vitro studies, [16] as well as the role of thyroid hormone on the growth and normal functioning of the male gonads. [16,17] Green tea is marketed commercially in Nigeria as tea bags, in various brand names.…”

“…Goitrogenic/anti-thyroidal effect of GTE, in relatively high doses has been reported in both in-vivo and in-vitro studies, [16] as well as the role of thyroid hormone on the growth and normal functioning of the male gonads. [16,17] Green tea is marketed commercially in Nigeria as tea bags, in various brand names. Green tea can taste sweet, bitter or astringent depending on the temperature of the water 60 o c water for sweet 80 o c for astringent and 100 o c of water for bitter tea respectively.…”