Catechin induced modulation in the activities of thyroid hormone synthesizing enzymes leading to hypothyroidism

Abstract

Catechins, the flavonoids found in abundance in green tea, have many beneficial health effects such as antioxidative, anticarcinogenic, anti-inflammatory, antiallergic, and hypotensive properties. However, flavonoids have antithyroid/goitrogenic effect, although less information is available about the effect of pure catechin on thyroid physiology. The present investigation has been undertaken to explore the effect of catechin administration on thyroid physiology in rat model. For the in vivo experiment catechin was injected intraperitoneally (i.p.) at doses of 10, 20 and 30 mg/kg body to male albino rats for 15 and 30 days, respectively, and thyroid activities were evaluated with respect to determination of serum levels of thyroid hormones, thyroid peroxidase, 5'-deiodinase I (5'-DI), and Na(+), K(+)-ATPase activities that are involved in the synthesis of thyroid hormone. Catechin decreased the activities of thyroid peroxidase and thyroidal 5'-deiodinase I, while Na(+), K(+)-ATPase activity significantly increased in dose-dependent manner; substantial decrease in serum T3 and T4 levels coupled with significant elevation of serum TSH were also noted. Histological examinations of the thyroid gland revealed marked hypertrophy and/or hyperplasia of the thyroid follicles with depleted colloid content. In in vitro study, short-term exposure of rat thyroid tissue to catechin at the concentrations of 0.10, 0.20, and 0.30 mg/ml leads to decrease in the activities of thyroid peroxidase and 5'-deiodinase I, while the activity of thyroidal Na(+), K(+)-ATPase remains unaltered even at high concentration of catechin treatment. The present study reinforces the concept that catechin, tea flavonoids possess potent antithyroid activity as evidenced from in vivo and in vitro studies.

Light and electron microscopic study of thyroid follicular cells in adult albino rats following green tea administration

“…Consistent with the above observations, a recent study carried out by Chandra and De [35] reported the antithyroid potential of GT catechins. They recorded a significant reduction in the serum levels of thyroid hormones and an increase in thyroid glandular weight accompanied by hypertrophic and hyperplastic changes of the thyroid follicles on administration of large doses of GT catechins.…”

“…In this regard, Chandra and De [35] postulated that catechin exposure reduced the activity of 5′-DI significantly, indicating that catechin may decrease the rate of conversion of T 4 to T 3 . The other thyroid hormone, T 3 , is secreted by the thyroid in a very small amount (∼13%) and the majority is formed in the peripheral tissues where T 4 is converted to T 3 by the activity of type-I 5′-monodeiodinase (5′-DI).…”

Flavonoid Rutin Increases Thyroid Iodide Uptake in Rats

“…Flavonoids were shown to have important effects in mammals, including antioxidant, estrogenic/antiestrogenic, antiproliferative and have been shown to decrease the risk for stroke [1–3]. Although flavonoids could have beneficial effects, there are data suggesting that some of them could interfere with the thyroid axis [4–8]. …”

“…Moreover, it has been demonstrated that some flavonoids could affect thyroid hormone action and transport [13]. It has also been shown that some flavonoids can inhibit D1 activity [8,14,15], while flavonoids, such as fisetin, quercetin and kaempferol, stimulate D2 activity in RMS-13 cells [16]. Some flavonoids have also been shown to modulate NIS function and expression in cell culture models [17,18].…”

Morphological and functional alterations of female reproduction after regular exposure of bamboo shoots of North East India

“…This effect could likely be due to the anti-thyroidal properties of BS which can induce hypothyroidism as patients with an underactive thyroid tend to have a very low basal metabolic rate; one of the most noticeable symptoms of hypothyroidism is weight gain and difficulty in losing extra weight [42]. Increase in TSH levels, thyroid weight as well as hyperplastic and hypertrophic nature of thyroid morphology on BS consumption are strong indicators of hypothyroidism induction [43]. A significant decrease in ovarian weight was also observed in comparison with the control group.…”