During the geochemical evolution of the Earth's crust took a significant amount of iodine leaching from most of the land 
surface in the oceans, so now the number of the element contained in the soil, is extremely small. Organisms living on the 
shores of the seas, not even eating seafood, well stocked with iodine because it - belongs to the volatile elements and can be 
acquired through the respiratory tract. It should also be noted that the iodine content in soils is inversely correlated with the 
height above sea level. 
Iodine is a member of thyroid hormones - thyroxine and triiodothyronine, which are characterized by a wide range of 
regulatory actions, particularly energy metabolism. The amount of iodine, which is used for the synthesis of thyroid hor-
mones, is about 0.4 mg per day calves weighing 40 kg, 1.3 mg - animals weighing 400 kg and 1.5 mg - calf cows. During 
lactation production of thyroid hormones in the thyroid gland grows: in highly productive cows on their synthesis consumes 
4-4.5 mg iodine per day. Production of thyroid hormones in the thyroid gland of cows increased when lowering the tempera-
ture, which leads to increased heat in the body. 
For a sufficient amount of iodine in feed about 20% of it is absorbed by the thyroid gland, where moderate iodine defi-
ciency in the diet of animals gland absorbs about 30%, and the low content - 65%. 
The need for iodine in lactating cows is about 0.8 - 1.0 mg per 1 kg of dry matter feed intake. Cash cow consume 3.5 - 
4.0 kg of dry matter of feed per 100 kg. Need mind that there are a number of feed containing hoytroheny - compounds that 
inhibit the synthesis and secretion of thyroid hormones that cause hypothyroidism. 
For lack of iodine in the diet of animals in the thyroid gland decreases production of thyroid hormones and slows the rate 
of oxidative processes. An important indicator of iodine deficiency is the increase of cancer because of hyper plastic thyroid 
hormone action. Negatively affect the body and excess iodine - there is hyperthyroidism. 
Iodine, received food from the body in the form of iodide is absorbed in the small intestine and in ruminants, except that 
- in the rumen. Since it easily penetrates the blood to various organs and tissues, partially depo in lipids. The most significant 
portion of iodine (70-80%), selectively absorbed by the thyroid gland. Iodide is oxidized to molecular iodine, which quickly 
binds to residues of thyroglobulin, forming mono- and one dyyodtyrozyn (phase transformation of inorganic to organic io-
dine). In phase condensation is the union of two dyyodtyrozyniv to form T 4  or one mono and one dyyodtyroz to form T 3 . 
The  main  factor  regulating  synthesis  of  thyroid  hormones,  TTG  is.  For  iodine  deficiency  is  insufficient  production  of 
hormones,  which  has  many  effects,  combined  term  "iodine  deficiency  disorders".  These  consequences  include:  goiter, 
hypothyroidism, growth retardation, impaired reproduction.  
Bold iodine from the body is carried out mainly by the kidneys (90 - 98%), because of its excretion in urine correlates 
with the supply of iodine.  
As a result, studies have found that the concentration of iodine in cows urine overwhelming majority (97.1%) was less 
than 70 mg/l, (2.9%) more, but in none of the studied animals not exceed 100 mg/l ( minimum standard). However, it should 
be  noted  that  none  of  the  studied  animals  in  clinical  studies  were  found  symptoms  of  hypothyroidism,  hyperthyroidism, 
goiter diseases. Obviously, this is due to compensatory capacities of the thyroid gland, which in part uses iodine deficiency as 
a result of its recycling (due to enhanced absorption of iodine from the blood). The iodine content in the urine of animals 
research group, which used potassium-iodide for two months, was in the range of 100 to 300 mg/l, and the watering to not 
exceed 70 mg/l. Thus, we achieved the optimum level of iodine in the body, which is confirmed by the determination of 
hormones.  
TTG  level  in  serum  of  animals  experimental  group  which  used  potassium  iodide  averaged  1,81 ±  0,132  mkMO/ml, 
which is 28.2% less compared with the control group (p <0.05). Content hormones T 3  and T 4  was higher by 14.0 and 17.3%. 
Thus, the increased content of thyroid stimulating hormone in cows in the control group shows the tension adenohypophysis 
compensatory  mechanisms to normalize the synthesis of hormones, so it is possible that prolonged iodine deficiency can 
cause the development of diffuse or nodular hyperplasia. 
It should be noted that in the case of potassium iodide within 60 days in the experimental cows observed "positive" 
normalization  dynamics  nutritional  status,  that  number  decreased  fat,  increased  milk  productivity,  increased  feed  intake, 
noted the positive impact on the sexual cycle. Gradual weight loss is not accompanied by increased levels of acetone bodies 
than early lactation.  
Conclusions and recommendations for further research. 1. The population of cows, heifers, calves of private sector is a 
state  of  iodine  deficiency,  but  lack  of  iodine  does  not  cause  clinically  significant  thyroid  cancer,  probably  due  to  its 
compensatory possibilities. 
2. Semi quantitative determination of urinary iodine is informative and one on the market of Ukraine. 
3. Add potassium iodide to the diet in recommended doses causes a positive effect on thyroid function, confirming the 
results of the research content of free fractions of T3 and T4. Improving their positive impact on the level of fatness and milk 
production. 
Prospects  for  further  research  are  ultrasound  and  histological  study  thyroid,  because  many  pathological  processes, 
including benign tumors, hormone levels may not change, iodine in the soil and feed and their antagonists - fluoride. 
Key words: Iodine, thyroid gland, thyroxin, triiodthyronine, cows, calves, heifers.