The effect of consuming large amounts of cassava leaves on thyroid fun
ction and urinary iodine was studied. Twenty volunteers were given 200
gm of boiled cassava leaves twice a day for 12 consecutive days. Thyr
oid hormones triiodothyronine and thyroxine were significantly lower b
y 9 days. Urinary iodine excretion was also significantly decreased. C
assava leaves, consumed in large amounts by aborigines, probably cause
d goitres by decreasing iodine absorption.