Biophysical effects of continuous X-rayon the level of serum thyroxin in hyperthyroidism patients

The thyroid hormones, thyroxin (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland primarily responsible for regulation of metabolism. An important component in the synthesis of thyroid hormones is iodine. The major form of thyroid hormone in the blood is thyroxin (T4), which has a longer half-life than T3. The ratio of T4 to T3 released into the blood is roughly (20 to 1). The level of thyroxin is affected by radiation. The aim of the study to determine and to assess the effects of continuous X-rays on thyroxin level in vitro quantitive measures. Thirty patients with hyperthyroidism disease were enrolled in this study. Blood samples were tested and irradiated by x-ray radiation source of total dose rate (0.4).Gry/sec. The level of thyroxin were determine before and after irradiation .The results showed that the level.of.thyroxine.are.significantly.reduced.(P<0.01).after.x-ray.irradiation. It is concluded that x-ray ionizing radiation, reduced thyroxin level by free radical forming and protein damaging. . Key word: Thyroxin, x-ray ,free radical . نيسكورياثلا ىوتسم ىلع ةرمتسملا ةينيسلا ةعشلال ةيجوليابلا ةيئايزيفلا تاريثأتلا نيسكورياثلا نومره زارفا طرفب نيباصملا دنع للهادبع نسح ةريمس كوكرك ـ ينقتلا دهعم لوبق خيرات :رشنلا 5 / 5 / 3102 ثحبلا ملاتسا خيرات : 30 / 3 / 3103 ةصلاخلا و نيسكورياث نيعون ىلع نوكي يذلاو ديورياثلا نومره ةيقردلا ةدغلا زرفت نينوريثلا دوي ثلاث وهو,دويلا نم يساسا لكشب عنصملاو نم لوطا يرمعلا هفصن يذلاو مدلا يف زرفنملا ديورياثلا نومره مظعم لثمي نيسكورياث. مسجلا يف يئاذغلا ضيلاا ميظنت نع لوؤسملا ثلاث نينوريثلا دوي ثلاث ةبسن ىلا نيسكورياثلا ةبسن نوكت ثيح نينوريثلا دوي 31 / 0 ا نومره ىوتسم رثأتي. نم فدهلا نا, عاعشلااب نيسكورياثل نيسكورياثلا نومره ىوتسم ىلع ةرمتسملا ةينيسلا ةعشلاا ريثأت مييقتو ديدحت وه ةساردلا هذه مسجلا جراخ يمك سايقب عاضخإ مت . ( 21 ث نمو جذامنلل نيسكورياثلا ةبسن رابتخا مت ثيح.نيسكورياثلا نومره زارفإ طرفب نيباصملا صاخشلأل مد نم جذومن) ةعشلااب تععش م ةعرجلا لدعمب ةرمتسملا ةينيسلا 1,0 نأب جئاتنلا ترهظأ. ةرمتسملا ةينيسلا ةعشلأاب نيسكورياثلا ريثأت ىدم ةفرعمل جذامنلا رابتخا مت .اث/ يرك نم لقا ةيلامتحلاا( حضاو لكشب ضفخنت نيسكورياثلا نومره ىوتسم 1,10 لك دنع ةرمتسملا ةينيسلا ةعشلأاب عيعشتلا دعب) نمز يف رييغت . ةعرجلا وأ ضرعتلا ةعشلاا نا ةساردلا هذه نم جتنتسن . ةينيسلا . للقي . نم . ىوتسم . نومره . نيسكورياثلا . نيوكتب . روذج . ةرح . ميطحتو .. .نيتوربلا . :ةلادلا تاملك Thyroxin ,x-ray ,free radical .


1-Thyroid hormone:
The thyroid hormones, thyroxin (T 4 ) and triiodothyronine (T 3 ), are tyrosine-based hormones produced by thethyroid glandprimarily responsiblefor regulation of metabolism. An important component in the synthesis of thyroid hormones is iodine.The major form of thyroid hormone in the blood is thyroxin (T 4 ), which has a longer half-life than T 3 . The atio of T 4 to T 3 released into the blood is roughly 20 to 1 [1 ]. Thyroxin is converted to the active T 3 (three to four times more potent han T 4 ) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T 1 a) and thyronamine (T 0 a) [2].

2-Production of the thyroid hormones:
. Thyroid hormones (T 4 and T 3 ) are produced by the follicular cells of the thyroid gland and are regulated by TSH made by the thyrotrophs of the anterior pituitary gland. Because the effects of T 4 in vivo are mediated via T 3 (T 4 is converted to T 3 in target tissues), T 3 is 3-to 5-fold more active than T 4 . Thyroxin (3, 5, 3', 5'-tetraiodothyronine) is produced by follicular cells of the thyroid gland. It is produced as the precursor thyroglobulin (this is not the same as TBG), which is cleaved by enzymes toproduceactive T 4 thyroxin is produced by attaching iodine atoms to the ring structures of tyrosine molecules.Thyroxine (T 4 ) contains four iodine atoms . Triiodothyronine (T 3 ) isidentical to T 4 , but it has one less iodine atom per molecule [3].Iodide is actively absorbed from the bloodstream by a process called iodide trapping.In this process, sodium is cotransported with iodide from the basolateral of the membrane intothe cell and then concentrated in the thyroid side follicles to about thirty times its concentration in the blood. Linking two moieties of DIT produces thyroxin combining one particle of MIT and one particle of DIT produces triiodothyronine. [4] . .

DIT + DIT → thyroxin (referred to as T 4 )
Proteases.digest.iodinated.thyroglobulin,releasing.the.hormones..T 4 .and.T 3 ,the.biologically.active .agents.central to metabolic regulation. Thyroxine is believed to be a prohormone and a reservoir for the most active and main thyroid hormone T 3 . T 4 is converted as required in the tissues by iodothyronine deiodinase. Deficiency of deiodinase can mimic an iodine deficiency. T 3 is more active than T 4 and is the final form of the hormone, though it is present in less quantity than T 4 [5 ].

3-Related.disease: :
Excess of thyroxin can cause (Hyperthyroidism) is the clinical disease caused by an excess of circulating free.thyroxin,free.triiodothyronine,or.both.Thyrotoxicosis is often used interchangeably with hyperthyroidism, but there are subtle differences. Although thyrotoxicosis also refers to an increase in circulating thyroid hormones, it can be caused by the intake of thyroxin tablets or by an over-active thyroid, whereas hyperthyroidism refers solely to an overactive thyroid [6 ].

4-Radiation:
The history of radiation begins with the discover of x-ray by wilhelm Roentgen in November 1895. The human being are exposed throughout their life.to.ionizing.radiation.this.radiation.comes.from.:  .
Ionizing radiation imparted to living systems can result in an array of biological endpoints including tissue injury, carcinogenesis and death. The initial step in this interaction of radiation with biological material is the deposition of energy to atoms and molecules which results in ionization and excitation [8] .Small quantity of energy from radiation exposure results from the non unifrom deposition of energy and through biochemical processes that amplify damage [9].
. Action of ionizing radiation on cells is two types: . 1-Direct action. 2-Indirect action 1-Direct actions : was occurred within milliseconds following irradiation , this type of action causes a number of physical and chemical events is used to describe the death of the cell [10] .
2-Indirect action: Since water is a major constituent of all biologic materials, water composes 80 % of the mass of biological systems; irradiation of water produces reactive chemical species that can damage biological molecules. These damage products may in turn initiate chemically reactive chain processes, with other biological molecules propagating further damage.
. When the cell is exposed to ionizing radiation, several responses may occur ranging from no detectable damage to cell death. Detrimental effects from low level radiation exposure and from chronic exposures may also manifest themselves long after the initial event. These effects can be divided into three areas of concern 1. Somatic .2. Genetic .3. Utero effects. [12] .

The aim of the study:
To determine and to assess the effects of continuous X-rays on thyroxin level in vitro quantitive measures.

Material and Methods
The study was carried on 30 patients with hyperthyroidism who attended Kirkuk General Hospital in Kirkuk city, for period from 1-09-2011 to01-12-2011.

Thyroxin level determination:
Each sample tested by TosoH analyzer instrument to know thyroxin level before and after irradiation .The normal range of T4 (4.9-11.0 µg /dl).

X-ray dose calculation:
The exposure can be calculated by the following equation:

Absorbed dose of air E (Ma/p) air
Where E is the mean photon energy (X-ray).
(M a/p) sub = mass energyabsorption coefficient for substance.
(M a/p) sub = mass energyabsorption coefficient for air. 1.30ml of serum at known thyroxin level (µg /dl) put in container where surface area is 4.9cm 2 .
The container put under the radiation source at distance 20cm in limited flied size of 2x2cm. The samples are irradiated at total doses of X-ray between (0.02-0.136Gy) and the exposure time between (0.40-2.75 sec).

Result & Discussion
A total number of 30 patients serum with hyperthyroidism disease irradiated by the Xray radiation..The level of T4 in blood samples were studied before and after irradiation.

1: Thyroxin (T4) level measurement:
The change in the level of thyroxin is clearly appeared after irradiation by X-ray. The level of thyroxin was significantly lowered (P< 0.01) after irradiation (table 1) in comparison with its level before irradiation. This reduction in the level of thyroxin is directly Proportional with the exposure time or X-ray dose at constant dose rate .These results are appear in figure (1).

2-Thyroxin level measurement before and after X-ray irradiation (for the same serum):
Serum has been divided in to five parts and every parts exposed to X-ray radiation at different exposure time . The measurements have been repeated three time and the mean is taken .The level of thyroxin before irradiation are shown in (table 2) which is significantly different from after irradiation P<0.01).The level of thyroxin is gradually reduced when exposed to X-ray radiation .This reduction is clearly appeared in this work and increased with increasing in the exposure time or X-ray dose at constant dose rate (fig 2).

Discussion
This study was aimed to assess the effects of X-ray radiation on thyroxin level and to find the most important factor in this radiation of changes in the thyroxin level.
In the present study the level of thyroxin is significantly reduced after irradiation when compared with the level before irradiation (P<0.01).The level of thyroxin was gradually reduced at each  1) (fig 2) .Our result were in agreement with [13].
The reduction in the level of thyroxin may be due to: 1-Free radical is formed by radiation, Free radicals may react with molecules of oxygen and such reactions are great radiobiological importance because they may lead to the production of peroxide radicals which causes biological damage, [14,15] . Thyroxin is derivative of amino acid. The x-ray causes damage in protein .by change in solubility and destruction in amino acid [16].