Problems of iodine and thiocyanate in domestic animals in goitrogenic areas of southern Poland.
High incidence of goitre in human together with low level of iodine in water and cow milk have been observed in Southern Poland (Table I). Therefore, iodine deficiency was considered as the only cause of goiter development. The correlation coefficient between iodine concentration in water and cow milk was r = 0.76 (Fig. 1) and indicate the possibility of iodine determination in milk instead of water. The iodine determination in milk reflects the level of iodine in water as well as in food, a negative correlation has been obtained between goitre incidence in human and iodine concentration in water (r = 0.43) (Fig. 2.). A low correlation coefficient suggest that iodine is not a solely factor responsible for goitre development. Studies on cows have indicated that thiocyanate may have effect on goitre development as well. There has been found higher concentration of thiocyanate (SCN) in blood plasma and in enlarged thyroids (Table II). Thiocyanate belongs to goitrogenic compounds and its main source are the plants of Brassica species widely cultivated in southern Poland. It has been found that cows fed with Brassica plants have high level of SCN both in blood and milk with no alteration of plasma iodine level. The transfer of iodine from plasma to milk is only slightly affected (Table III). The level of SCN in the thyroid depends on its plasma concentration; the calculated correlation coefficient is r = 0.88 (Fig. 3). Enhanced thyrotropin (TSH) secretion (during goitrogenesis) may be accompanied by increased accumulation of SCN in the thyroid (like iodide) and reduced oxidation to SO4 (unlike iodide) (Fig. 4). Therefore we postulated that TSH may be partly responsible for increased SCN level in goitrous thyroids. The question arise whether increased ingestion of SCN does really potentiate iodine deficiency and goitrogenic process in animals breeding in southern Poland. For explanation some additionally experiments were performed on laboratory animals. It have been observed that enhanced level of plasma SCN following feeding with Brassica plants increased proportionally the goitrogenic action as well as the accumulation of 131J by the thyroid and its conversion into organic form (Fig. 5). The latter data was confirmed by positive correlation between thyroxine and plasma SCN levels in sheep (r = 0.49), (Fig. 6) Thiocyanate like other monovalent anions suppress goitrogenic effect of propylthiouracil. However, anti-goitrogenic properties of SCN depends on normal iodine ingestion (Fig. 7).(ABSTRACT TRUNCATED AT 400 WORDS)