Veterinary
science / 1. Veterinary medicine
Functional
disorders of the animal thyroid gland
Master
of veterinary sciences Raketsky V.A.
Kostanay
state university of A.Baytursynov, Kazakhstan
Violation of the
thyroid hormone output is the cause of different diseases. The special shape of
hypotheriosis is hypothyroidism. The term ‘thyrocele’ usually means the thyroid
gland rising, which can be due to different reasons. Hypothyroidism appears in the
definite geographic areas where available food resources lack necessary amounts
of the iodine. The probability of autogenous iodine insufficiency is also
possible due to the malabsorption and iodine fixation. Iodine deficiency leads
to a synthesis decrease of the thyroid hormone that, according to the feedback
mechanism, strengthens TSH secretion by pituitary organ and promotes the
thyroid body hypertrophy. These processes begin to make compensation for the
hormone deficiency, but under the condition of iodine deficiency the synthesis
of number of needed hormones fails even in enlarged gland, and the
hypothyroidism develops, which may lead to myxedema and congenital myxedema in
the difficult and go far cases [1]. From anatomicopathological point of view,
hypertrophy and hyperplasia of the thyroidal epithelium are based at the heart
of hypothyroidism in concordance with the well significant vegetations of the
thyroid stroma and also microvasculature displacement. The colloid retention
also plays a significant role in the thyroid body, typically moving to the
forefront (colloid goiter). Being a long-lasting pathologic process, the
colloid goiter, as a rule, has a difficult and tessellated histoarchitecture
where different pathological evidences of the specific thyroid secretion and
also dystrophic changes can be observed, it sometimes leads to the death of the
parenchyma locuses, subsequently replaced by the connective vegetations. There
may be the signs of the mineral metabolism frustration in the thyroid tissues,
in particular calcinosis, which can be either cellicolous with the loss of
calcium salts in the thyrocyte dystrophic changes. The reason of these changes
can be hypercalcemia along with the calcitonin deficiency or excessive
production of the parathormone [2].
Sporadic goiter is
a specific clinical shape and occurs in people living within the non-endemic
goiter areas. From the perspective view of the doctrine of microelementosis, it
refers to the iodine deficient state. It is in this form recorded: 1) the
goitrogenic agents intake, preventing the iodine disposal by the thyroid gland;
2) the liver and gastro-intestinal tract involvements, interrupting the
absorption and metabolism of iodine; 3) the iodine intake is out of reach for
absorbing (high content of the goitrogenic agents in the water and soil); 4)
the violation of the intrathyroid
iodine and hormone biosynthesis due to a congenital diminution of the thyrocyte
capacity to absorb and deposit of iodine; the deficiency of the enzyme systems
in the iodide oxidation in the atomic iodine; the violation of a convention
of iodtyrosines to iodtyronines [3].
Etiology of the sporadic goiter hasn’t been established once and for all. The
progress of the sporadic goiter associated with the action of some endogenous
factors, basically of the genetic order (enzyme system deficiency, leading to a
decrease in the absorption and fixation of iodine by the thyroid gland, a
biosynthesis violation of the thyroid hormones, as well as a violation of the
thyroid hormone use on the periphery, etc.). An excess of high-thiocyanate
(goitrigène) food (cabbage, beets, turnips, soya, etc.) contributes to
the progress of the sporadic goiter, under influence of which the inclusion of
iodine in the thyroid gland and hormone biosynthesis is decreased. Thyroid
hormone deficiency, both in the endemic and sporadic goiter, leads to an
increased secretion of the thyroid-stimulating hormone, calling hyperplasia of
the thyroid gland tissue - with the development of goiter. Except for the primary
hypotheriosis, there are known infrequent cases of the synthesis inefficiency
in the thyroid-stimulating hormone (postprimary hypothyroidism) and TSH
releasing factor (tertiary hypothyroidism). There are also thyroid gland
diseases, relating to the dysfunction of immune system [4]. In the USA, for
example, one of the most common causes of the hypotheriosis and goiter in
children is the autoimmune thyroid gland involvement (Hashimoto disease), when
the blood of patients produces antibodies to microsomes of the thyroid and
thyroglobulin. The term ‘autoimmune thyroid gland disease’ unites the sequence
of states with very different clinical and laboratory signs. To the autoimmune
thyroid gland disease refers: autoimmune hyperthyroidism (Graves disease, Basedow's
disease), immunologic thyroiditis (Hashimoto's thyroiditis and other) [4]. Immune disorders
are encounted in other diseases of the thyroid gland (for example, acute
nonsuppurative thyroiditis, nontoxic nodular goiter and papilliferous
carcinoma),however, they are postprimary over there, and therefore these
diseases are not related to autoimmune [5,6]. Disorders in the system of
immunoregulation, causing the development of the thyroid gland autoimmune
disease, are somewhat associated with the environmental factors [5]. Some
authors consider that the appearance of the thyroid gland autoimmune disease
plays a significant role in the bacillosis. A trigger function was attributed
to a great number of micro organisms, but a special attention is paid to Yersinia enterocoliticae (Y.e.)[5]. In summary, the development
of the thyroid
gland autoimmune disease is impossible without the immune system disorders.
List of used information resources:
1. Hamitova A.M.
Hypothyrosis and its preventive care /À.Ì.Hamitova, À.N.Yunusova. - Kazan,
1979. - 80 p.
2. Àlyoshin B.V. Hypothalamus and thyroid gland
/B.V.Alyoshin, V.I.Gubitskiy. - Ì.: Medicine, 1983.
- 184 p.
3. Heppner D.F.
Biosynthesis and hormone secretion // Endocrinology and metabolism: English
translation / Under the editorship of F. Fleming, D.D.Backster, A.E.Brodus,
L.A.Fromin. In 2. V.1.-Ì.: Medicine,
1985.-P. 273.
4. Bakhmetyev B.A The
effect of thyroxine on certain stages of immunogenesis: Author's thesis.... Cand. Med. Sc. Perm. 1986. -20
p.
5. Volpe R. Autoimmune
diseases of the endocrine system /R.Volpe //CRC, Boca Raton. 1990. P. 1-364.