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.
ABSTRACT
Green tea, prepared from the steamed and dried leaves of the shrub Camellia sinensis, is known for its antioxidant and anti-carcinogenic effects. However, its effects on male gonadal functions have not been explored adequately and the present investigation has been undertaken to evaluate the effect of green tea extract on gonads of adult male albino rats. Results of in vivo studies showed that green tea extract (GTE) at mild (1.25 g%, ≡ 5 cups of tea/day), moderate (2.5 g%, ≡ 10 cups of tea/day) and high (5.0 g%, ≡ 20 cups of tea/day) doses, for a period of 26 days, altered morphology and histology of testis and accessory sex organs. A significant dose-dependent decrease in the sperm counts, inhibited activities of testicular ∆53- and 17-hydroxysteroid dehydrogenase (∆5-3-HSD and 17-HSD respectively) and decreased serum testosterone level were noticed. Significant increase in serum LH level was observed after moderate and high doses; serum FSH level also increased but not significantly. Histopathological examination showed inhibition of spermatogenesis evidenced by preferential loss of matured and elongated spermatids. Results of this study showed that GTE at relatively high dose may cause impairment of both the morphological and normal functional status of testis in rodents and thus its consumption at relatively high doses raises concern on male reproductive function in spite of its other beneficial effects.