Effect of cassava (<i>Manihot esculenta crentz</i>) on thyroid status under conditions of varying iodine intake in rats

Abstract

Cassava (Manihot esculenta Crantz), a widely used common vegetable of Indian origin contains dietary goitrogens. Goitrogenic content, in vitro anti-thyroidal activity and in vivo antithyroid potential of fresh and cooked cassava of Indian origin in albino rats with and without iodine supplementation were evaluated in this study. In vitro inhibition of thyroid peroxidase (TPO )activity was found with fresh and cooked cassava extract but the presence of extra iodide in the incubation media had shown reduction in such inhibition to an extent. Inhibition constant (IC 50 ) and PTU equivalence of fresh cassava were 42.5 ± 1.35µg and 2.21 respectively. After consumption, cyanogenic constituents in cassava are metabolized to thiocyanate and iodine-retaining capacity seems to be dependent on thiocyanate exposure. In cassava fed rats, the urinary iodine concentration resembled the state of adequate iodine nutriture but thyroid gland fails to utilize available iodine. Increased thyroid weight (P < 0.001), inhibited thyroid peroxidase (TPO) activity and reduced thyroid hormone profiles (P < 0.001) were noted in fresh and cooked cassava fed rats, resembling a relative state of morphological as well as biochemical hypothyroidism even in presence of adequate iodine.

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

“…The cyanogenic glycosides and glucosinolates present in BS are readily converted to thiocyanates which appear in the blood and urine [22]. The free thiocyanate present in BS also adds to these levels.…”

“…BS however contains an approximate 600 mg/kg wet weight of cyanogenic glycosides of the taxiphyllin group, glucosinolates and thiocyanates [22]. All these are anti-thyroid components of naturally occurring goitrogenic plants and are capable of disrupting the bodies' ability to utilize iodine, blocking thyroid hormone synthesis and release [22]. Thus, being an established anti-thyroidal agent it is expected to bring about changes by perturbing balance of the hypothalamo-pituitary-thyroid axis and hypothalamo-pituitary-ovarian axis or by any of its several other components which in their way can impinge on the female reproductive functions.…”

“…It contains carbohydrates (5.70%), proteins (3.90%), minerals (1.10%) while several other essential components such as vitamins, amino acids, sterols, polyphenols and steroids can be extracted from it to a lesser extent [40]. BS however contains an approximate 600 mg/kg wet weight of cyanogenic glycosides of the taxiphyllin group, glucosinolates and thiocyanates [22]. All these are anti-thyroid components of naturally occurring goitrogenic plants and are capable of disrupting the bodies' ability to utilize iodine, blocking thyroid hormone synthesis and release [22].…”

“…The rats were allowed free access to drink water and were fed on standardized normal laboratory diet (20% protein) which consisted of 70% wheat, 20% Bengal gram, 5% fish meal powder, 4% dry yeast powder, 0.75% refined til oil and 0.25% shark liver oil with required amount of potassium iodide [29]. Control rats were fed a normal laboratory diet and experimental group was fed BS as mentioned below for 45 d. [22] The experimental group of rats was fed BS by replacing 1/3rd portion of normal diet. Sixty gram of BS were weighed, equal amount of water was added to it and boiled for 15 min.…”

“…Recent studies have also revealed that BS has a number of health perks: increasing appetite and digestion, reducing obesity and risks of cardiovascular disease [16] as well as anti-cancer constituents [17][18][19][20]. In opposition to all the nutraceutical advantages of BS, it is an acknowledged natural goitrogen with anti-thyroidal constituents like cyanogenic glycosides [21], glucosinolates and thiocyanates [22] and has been reported to cause endemic goiter in Manipur, North East, and India on regular consumption even in presence of adequate iodine [23]. Hypothalamic-pituitary-thyroid axis and hypothalamicpituitary-ovarian axis function in close conjunction and as thyroid hormone receptors exist in the ovarian tissue; several instances of hypothyroidism causing reproductive disturbances are available including menstrual cycles characterized mainly by polymenorrhea, especially anovulatory cycles [24] and an increase in fetal wastage in mature women [25].…”