Physiology Practic PDF

1 je THE DIGESTIVE EFFECT OF SALIVA ON STARCH The digestion of starch begins in the mouth, where it is mixed with saliva containing the ptyalin. Starch is hydrolyzed in several shorter polysaccharides (amylodextrines, e...

1 je THE DIGESTIVE EFFECT OF SALIVA ON STARCH The digestion of starch begins in the mouth, where it is mixed with saliva containing the ptyalin. Starch is hydrolyzed in several shorter polysaccharides (amylodextrines, erythrodextrines, acrodextrines and finaly maltose which is a dissacharide). Each of these steps can be recognized using an identification reaction with Lugol solution.The final digestion product of starch is maltose and can be identified using the Trommer reaction. OBJECTIVE: To understand and explain the action of salivary amylase and how can we demonstrate its action. Limits in salivary amilase action on starch. Understand and explain the factors which can influence the amylase activity (temperature, pH) MATERIALS 1. Starch solution 1%0 2. Iodine (Lugol reagent) (contains iodine, potassium and water 1:2:300) 1% 3. Test tubes 4. Graduated glass cylinders 5. Saliva 6. NaOH 7. CuSO4 10% solution 8. Filter paper PROCEDURE: Take 6 clean test tubes and add 5 ml of starch solution in each tube and 2-3 drops of Lugol solution (I + KI). Notice the colour and keep the first tube (T1) as control. Proceed as follows with next tubes: T2 – add 0,5 ml of boiled saliva. Due to inactivation of ptyalin by heat, there is no colour change T3 – add 3 ml of fresh saliva and wait for 2-3 minutes, then heat the tube to intrerrupt the reaction. T4 – add 3 ml of fresh saliva and wait for 5-7 minutes, then heat the tube to intrerrupt the reaction. T5 – add ml of saliva, wait for 15-20 minutes and then heat the tube to intrerrupt the reaction. T6 – proceed as before and wait for 30 minutes for the complete digestion of starch to maltose. Observe that each stage of starch digestion is related with different colours of the solution: amilodextrine blue-violet (T3), erythrodextrine pink-violet (T4), acrodextrine – colourless (T5). The complete digestion to maltose produces a colourless solution (T6). Test tubes 1 - 6 TROMMER REACTION PRINCIPLE: In alkaline pH and by heating, the maltose reduces the CuSO4 solution in cuprous oxid. MATERIALS 1. test tubes 2. gas burner 3. NaOH 20% solution, CuSO4 10% solution, starch solution 4. saliva PROCEDURE: In a test tube add 3-4 ml from maltose solution and an equal volume of NaOH, homogenize, and add drop by drop CuSO4 solution, obtaining an unsoluble blue precipitate. Boil the precipitate and notice the appearance of a red-cooper precipitate at the bottom of the tube. 2 MINERALS EVIDENCE IN SALIVA CALCIUM (from calcium salts) MATERIALS : test tube, ammonium oxalate 10%, saliva, microscope PROCEDURE: take 3-4 ml of saliva in a test tube, add 3-4 drops of ammonium oxalate. In the presence of Calcium, a white unsoluble precipitate appears at the bottom of the tube. Collect a drop of precipitate, put on a glass slide, dry and examine to microscope. The presence of octaedric cristals is related with calcium oxalate formation. 3 MINERALS EVIDENCE IN SALIVA PHOSPHORUS (from phosphates) MATERIALS : test tubes, gas burner, saliva, HNO3 (nitrogen acid), 12(NH4)2 MoO4 (ammonium molibdate). PROCEDURE: take 3-4 ml of saliva in a test tube , add 3-4 drops of HNO3 and ammonium molibdate in excess. Heat carrefuly the tube and notice the appearance of a yellow precipitate (phospho ammonium molybdate). Na2(PO4)3 + 12(NH4)2 MoO4 + 21 HNO3 = (NH4)3H4[(PMo2O7)6] + 21 NH4NO3 + 10 H2O Y MINERALS EVIDENCE IN SALIVA KSCN (Potassium sulfocyanate) MATERIALS: test tube, FeCl3 (ferric chloride) 3%, HCl (hydrochloric acid) 10%, saliva PROCEDURE: take 3-4 ml of saliva in a test tube, add 1-2 drops of HC land 1-2 drops of FeCl3. A brick-red precipitate of ferric sulfocyanate appears. The SCN- ion is found in saliva in concentration of 0,01-0,03 mg%. It is an excretory product, resulted from proteic metabolism or fruit ingestion. This is an detoxification mechanism. The SCN- concentration increases in smokers saliva. KSCN in the saliva of non-smokers (left) compared to smokers (right). There is an increased concentration of KSCN in smokers that is identified by a stronger, darker color. S GASTRIC JUICE COLLECTING In humans gastric aspiration using an Einthorn tube or endoscope is the most common method. GASTRIC JUICE SECRETION can be stimulated clinically using specifical stimulators: histamin, histalog ( a synthetic analogue), pentagastrin, insulin. The HCl secretion rate is usefull in gastric ulcer investigation. a. The maximal stimulatory test using Histamin was introduced by Kay in 1953; PROCEDURE: 24 h before the test, remove the antiacid and anticholinergic theraphy. In the morning of the test, pass the Einthorn tube through the esofagus into the stomach. Aspire the gastric stasis using 20 ml siringe and collect the basal secretion for 1 hour. Then inject an antihistaminic drug (which doesn’t influence the gastric secretion but prevents the possible adverse events of histamin), followed by the histamin phosphate administration, 0,04 mg /kg body weight. Collect the gastric secretion samples from 15 to 15 minutes for another hour. The HCl will be measured in each sample and results are noted in a table. INTERPRETATION Histamin stimulates the HCl acid secretion in normo and hyperreactive persons, but doesn’t produce a response in atrophic gastritis. Following its description by Kowalewski in 1949 and then by Kay in 1953, the augmented histamine test was introduced into routine clinical practice. Histamine was administered in a dose of 40 µg/kg in this test. Previously histamine was applied in lower doses but this did not produce maximal acid output. After intravenous or subcutaneous administration of dose 40 µg/kg/h, histamine can induce acid secretion reaching maximal acid output. This dose was established as a standard in further investigations. After histamine administration the peak secretory effect usually occurred during the first postinjection hour. Even though the protective treatment preceeds the histamin administration, some adverse events can appear: headache, tachicardia, hypoptension, abdominal pains, gastric hemorrhage. b. Histalog test has the same significance and the advantages that it doesn’n neccesits previous treatment with antihistaminics and the adverse events are rare. c. Insulin test (Hollander) is based on the stimulative role of hypoglycemia - induced with insulin- on gastric secretion, due to vagus dorsal nucleus stimulation. This test provides information about the efficacy of vagotomy in gastric ulcer operated patients. For all tests, the gastric acid flow has to be determined. d. Pentagastrin was approved in 1967as a stimulant of gastric acid secretion instead of histamine. Pentagastrin appeared to be safer for patients and the secretory response to pentagastrin was found to be identical to that of gastrin and histamine e. Ethanol and caffeine were previously employed as stimulators for gastric acid secretion. The response of a stomach to ethanol or caffeine was much smaller, as compared to pentagastrin, histamine or a meal. Therefore, ethanol and caffeine are no longer used for routine gastric secretory testing in humans. Normal and pathological HCl secretion BASAL MAXIMAL STIMULATION Volume Basal acid flow Volume Maximal acid flow (ml) mEq/hour (ml) mEq/hour Normal 50 2,2 + 1,5 200 20 + 4 Gastric ulcer 40-50 1,2 + 0,5 200-250 14+ 6 Duodenal ulcer 80-100 3,5 + 2 300-350 30 + 10 6 HCL ACID DOSAGE IN GASTRIC JUICE The gastric juice acidity is expressed into mEq/l of HCl or into mEq/h, representing the basal acid flow. In the gastric juice, HCl exists in two froms: free and combined (with different proteins). PRINCIPLE: Using titrimetric method, the gastric juice acidity is neutralized by a NaOH n/10 solution, in the presence of fenolftalein and Topffer reactive (0, 25 para dymethylaminobenzen in alchohol) as indicators. MATERIALS: NaOH n/10, Topffer reactive, fenolftalein 1% in alchohol, pipets, Erlenmeyer glasses, test tubes, burette. The Topffer reactive has yellow-orange colour. The free HCl turns the colour into red. PROCEDURE: Take 10 ml of gastric juice in an Erlenmeyer glass and add 3-4 drops of Topffer reactive. In the presence of free HCl the solution turns into red. Add from burette drop by drop NaOH n/10, till the colour turns into yellow-orange. Note the number of used ml of NaOH solution to neutralize the free HCl with N1. Add 2- drops of fenolftalein and continue the titration until the colour turns into pink, indicating the boung HCl neutralization and an excess of NaOH. Note the number of ml NaOH used to neutralize the combined HCl with N2. The total acidity = N1 +N2 The results will be expressed into clinical units (the number of ml from NaOH n/10 solution used to neutralize the HCl from 100 ml gastrci juice) or into grams HCl for 100 or 1000ml gastric juice. Calculation for Clinical Units (Javorski): Free HCl = N1 x 10 C.U. Combined HCl = N2 x10 C.U. Total HCl = (N1+N2) x 10 C. U. Calculation for grams of HCl /1000 ml: use the equivalent gram of HCl solution n/10 = 0,00365. Free HCl = N1 x 0,00365 x 100 g HCl %0 Combined HCl = N2 x 0,00365 x 100 g HCl %0 Total HCl = (N1+N2) x 0,00365 x 100 g HCl %0 The normal values of gastric juice acidity are: C.U. g %0 Free HCl 15 1 Combined HCl 25 1-2,5 Total HCl 40 2-3,5 Calculation in mEq/l: 1Eq HCl = 36,5 g 1mEq HCl = 0,0365 g Free Acidity in mEq/l = N1 x 0,00365 x 100/0,0365 = N1 x 10 Combined Acidity in mEq/l = N2 x 0,00365 x 100/0,0365 = N2 x 10 Total acidity in mEq/l = (N1+ N2) x 0,00365 x 100/0,0365 The normal value for the total acidity = 100-120 mEq/l. Gastric acidity in different diseases 7 THE EVIDENCE OF FREE HCl ACID IN GASTRIC JUICE PRINCIPLE: Heat till evaporation gastric juice in the presence of fluoroglucin solution MATERIALS: porcelain capsula, filtered gastrci juice, gas burner, Gunsburg reactive (alchoholic solution of vanilin and fluroglucin). PROCEDURE: Add on a porcelain capsula few drops of gastric juice and then 3-4 drops of Gunsburg reactive. Heat in small flame. In the presence of free HCl in gastric juice, a red colour will appear. The free HCl determination should be done using fresh gastric juice, because free HCl volatilizes. 8 THE LACTIC ACID EVIDENCE IN GASTRIC JUICE THE BERG REACTION PRINCIPLE: Lactic acid is not a normal compound of gastric juice. It can appear only in pathological statuses, characterize by the decreasing of HCl secretion. In hypo/anacidity, the intestinal bacterial flora advances into stomach producing a contamination.. In this conditions, the glucose from food will be transformed by bacteria into lactic acid. The hypo/anacidity is a high risk status because of its association with gastric cancer and pyloric stenosis. MATERIALS: Berg reactive (FeCl3 solution 30% in acidic solution), test tubes, gastric juice PROCEDURE: in the presence of ferric salts, lactic acid gives iron lactate which is yellow. Take 8-10 ml of Berg reactive in a test tube and add 2 ml of gastric juice. In the presence of lactic acid, the solution turns into yellow. THE UFFALMAN REACTION MATERIALS: Uffalman reactive (FeCl3 solution 30% in phenol 4%), test tubes, gastric juice. Uffalman reactive is violet. PROCEDURE: Take 5-6 ml of Uffalman reactive in a test tube and add 1 ml of gastric juice. In the presence of lactic acid, the solution turns from violet into yellow. 9 Determination of the gastric rennin Gastric renin (labferment, chymosin) in the gastric juice of newborns has a role in the coagulation of casein in milk. The optimal pH of action of renin is between 4.5-5.5. Principle: milk casein, with isoelectric point at pH 4.6, under the action of the gastric rennin, is transformed into paracasein, which in the presence of Ca ions , is transformed into calcium paracaseinate (curd). To demonstrate this action that takes place in phases, we do the following experiment: Materials needed: test tubes, thermostat, 10% calcium chloride solution, 1% gastric rennin solution and milk. Procedure: take 4 tubes in which 4 ml of milk are introduced. 1. In the first test tube, 0.5 ml of the gastric rennin solution is added to the milk, it is left in the thermostat at 38 ° C, after 30 minutes the coagulation of casein is observed through the curd formed in the test tube. 2. In the second test tube, add over the milk 0.5 ml of gastric rennin solution which has previously been inactivated by boiling. Leaving the tube on the thermostat at 38°C does not cause coagulation. 3. In the 3rd test tube, add 1 ml of potassium oxalate solution to the milk to block the calcium ions and then add the gastric rennin. Leave the tube on the thermostat at 38° C for 30 minutes. Coagulation does not take place. 4. In the 4th test tube, add 1 ml of 1% potassium oxalate, 0.5 ml gastric rennin over the milk, leave the test tube to the thermostat at 38° C for 30 minutes. Coagulation does not take place. Add 1 ml of calcium chloride solution, it is observed that coagulation occurs immediately. These experiences explain the two phases that take place in the casein coagulation process. 1. Phase I: casein from milk, under the action of the gastric rennin passes into paracaseinate, which is soluble. This phase does not require the presence of calcium ions. 2. Phase II: soluble paracasein, in the presence of calcium ions passes into calcium paracaseinate, which is insoluble and constitutes the curd. Gastric lipase hydrolyzes only finely emulsified fats into fatty acids and glycerol. It acts in a weakly acidic environment; The optimal pH of activity is between 4-5. Its action is obvious in infants, where the pH of gastric juice is weakly acidic (pH = 4.5-5.5).  p HAY REACTION PRINCIPLE: The emulsification is base don the property of the bile salts to reduce the superficial tension forces between water and fats. MATERIALS: test tubes, oil, bile salts solution (urine or diluted bile), sulphur flower (powder) PROCEDURE: Take 3-4 ml of solution containing the bile salts into a test tube and pure water in another and intersperse some sulphur flower in both. After few minutes, in the presence of bile salts the sulphur flower falls at the bottom of the tube (right). In the absence of the bile salts, the sulphur flower remains at liquid surface (left). 11 ROSENBACH REACTION (BILE PIGMENTS IDENTIFICATION) MATERIALS – filter paper, bile pigments solution (bile), concentrated nitric acid HNO3, sodium nitrite cristals (NaNO2) PROCEDURE: drip 2-3 drops from bile solution on the filter paper. In the middle of the spot add 1 drop of nitrogen acid. Around the last drop. Some concentric rings appear: yellow- red, violet-blue and green. The last one is characteristic for bilirubin presence. 12 URINARY AMYLASE DETERMINATION PRINCIPLE: Amylase is filtered by kidney and can be eliminated by urine. In acute pancreatitis the hyperamylasemia is characterised by an increased activity in plasma of pancreatic amylase. In this disease, the activity of the pancreatic amylase varies within wide limits, from within the reference range to more than 50 times the upper reference limit, according to the functional state of the pancreas, the severity, and cause of the inflammation. During the following 4 -10 days the pancreatic amylase activity gradually decreases to normal level. The half-time of pancreatic isoamylase activity in plasma is about 12 hours. The same profile appears in urine and can be determined using the Wohlgemuth method. Anyway, due to variation of the diuresis the reference ranges for analytes in urine are much wider than the corresponding ranges in plasma. Thus, it must be concluded that urine has some disadvantages as compared to plasma/serum as system for determination of amylase activity In chronic pancreatitis with exocrine pancreatic insufficiency the amylase is greatly decreased. MATERIALS – 10 test tubes, urine, starch solution 1%0, Lugol solution PROCEDURE: In the first tube add 2 ml of urine, and in the other 9 add 1 ml of NaCl 0,9% in each. From the first tube take 1 ml of urine and add it into the second one; than take 1 ml from the second and add it into the third one and continue to obtain progressive dilutions of urine in all test tubes. Discard 1 ml from the last tube test. In this way you will obtain next dilutions: 1/1. 1/2, 1/4., 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512. In each tube add 2 ml of starch solution 1%0 (which means 2 mg of starch) and put the tube sat thermostate at 37ºC for 30 minutes. After 30’ cool the tubes under cold water and add 4 drops od iodide solution each. The test tubes containing the undigested strach will be blue, instead the tubes with digested starch will be colorless. Note the last colorless tube , which contains enough amylase to digest 2 mg of starch. Express the result in Wohlgemuth units.  One Wohlgemuth Unit represents the amount of amylase which can hydrolyse 1 mg of starch at 37ºC in 30 minutes. It means that the noted tube test contains 2 WU. If this tube is the sixth, the dilution is 1/32. If this dilution of 1/32 contains 2 UW, it means that the undiluted urine contains 2x32 = 64 UW. The amylase determination has to be done in 24 h urine. The normal value for urinary amylase is 32-64 UW and for plasma amylase is 16-32 UW. 1 2 3 4 5 6 7 8 9 10 13 THE RADIOLOGICAL EXPLORATION OF THE PITUITARY GLAND The pituitary pathology is mainly tumoral (adenomas). A growing tumor ussualy compress the bone, creates erosion and invasion of the sphenoidal bone. The normal sella turcica is delimited by the anterior, respectivelly posterior clinoidal processes and during tumoral expansion, these elements can be modified or can dissapear as anatomical reference point. These injuries can be visualised using X-rays, discovered by Roentgen (1895). SKULL X RAY – LATERAL X-rays pass through the body structures and project a shadow of the contents of the body onto the detectors; the projection appears in various shades of gray and only reveals bones clearly, while soft tissue just appears black. A main disadvantage is that the three-dimensional body parts are projected onto two-dimensional film, losing valuable information. The method can visualise the bonny walls of the sella turcica; the sella turcica normal diameters are: 15/12/19 mm (lenght, depth şi width). The normal image changes represents the base for pituitary adenoma diagnosis and classification. Skull X ray; white arrows show sella turcica COMPUTERIZED TOMOGRAPHY Hounsfield introduced CT in 1971. He was awarded the Nobel Prize for this invention in 1979. Principle: CT was originally proposed and used as an extension of the basic X-ray. The CT methodology uses a X-ray tube and detectors rotate around the patient, with the axis of rotation running from the patient’s head to toe. It is based on the fact that X-ray absorption is proportional to density of the structures they go through to obtain a density profile of a body slice (transverse or axial cut). Radiation detection system is composed of detection elements, such as scintillating crystals and photodiodes. Computer reconstructs the image from raw scan data then a picture is created by a cathode ray tube. CT is a low-risk procedure, but can be accompanied by allergic reaction to contrast dye. It uses more radiation than modern standard X-Ray, but still minimal amount. On CT, bone appears white; gases and liquids are black and tissues are gray. CT gives a tomodensitometric analyse of the content of sella turcica (the pituitary tissue structure). The normal pituitary gland may also have a nonhomogeneous CT appearance with intermingled lucent and dense areas. This heterogeneity is related in part to microscopic variation within the anterior and posterior lobes. A contrast dye enhances the image contrast and faciltates the delimitation of tumors by the surrounding tissue. CT -Normal pituitary gland CT – Pituitary adenoma MAGNETIC RESONANCE IMAGING (MRI) uses the magnetic properties of hydrogen and its interaction with a large external magnetic field. MRI is performed with examined part of the patient centered in a magnetic field much stronger than the field generated by the earth or by a normal magnet. In this case, most hydrogen atoms (protons) contained in body water tend to fall into line with this magnetic field. The second step is to apply pulsed radio waves of short duration to modify proton orientation. Protons have the tendency to return to their initial alignment, with emission of radio waves of specific frequency; these radio waves are detected by an antenna placed around the patient. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. A contrast material might be injected to improve the quality of the image. MRI views may be obtained in any plane of space, whereas CT-scan native images are only transverse. MRI does not generate any X-rays and no harmful biological effects have ever been proved under standard examination conditions. However, magnetic field interacts with metallic objects, resulting in image degradation. As any iron object is strongly attracted by the magnet, security precautions need to be respected as mentioned above. MRI is the best imaging test to identify pituitary tumors of all types. MRI can identify a macroadenoma of the pituitary gland, as well as most microadenomas. But the MRI may not be able to detect microadenomas that are smaller than 3 mm. Advantages of these systems are a relatively low cost, no electricity, no irradiation. Between 5% and 25% of healthy people have some minor abnormality of the pituitary gland that shows up on an MRI scan. Normal head MRI showing a sagittal view through the pituitary gland. The large arrow indicates the anterior portion of the pituitary gland, whereas the small arrow indicates the posterior (normally whiter) portion of the pituitary gland. (B) Coronal head MRI with posterior pituitary bright spot noted ectopically at the base of the hypothalamus (arrow). (C) Sagittal MRI view of an infant pituitary gland showing a transected hypothalamic-pituitary stalk (arrow). 14 THYROID SCINTIGRAM The method represents a nuclear medicine investigation. Different types of nuclear medicine are: histogram mode, list mode, synchronized recordings and three dimensional reconstruction (SPECT and PET). Histogram Mode: In this mode the viewing area of the gamma camera is divided into a matrix of picture elements (pixels). The pixels become darker (or more red) by adding more pictures of the same place by time. This method can be used to examine the activity distribution in the target organ. Histogram mode is based on a predefined time interval. Three Dimensional Reconstruction: In this mode images obtained with a rotating gamma camera (multiple two dimensional) will be processed to render a three dimensional image similar to the process in CT scan. The procedure is called single photon emission computed tomography (SPECT). A more accurate way to obtain two and three dimensional images is positron emission tomography (PET) where positron emitting isotopes are used. These isotopes combine quickly with an electron and two gamma quanta are emitted in opposite direction. By detecting both quanta the location of the emission can be measured. For the thyroid scintigram, the histogram mode is most used. Principle: During nuclear medicine examination, the radioactive labeled material is injected. The radiation of the radioactive material can be detected by a gamma-camera which is sends the information to a computer for further processing.It is better to use an isotope with a relatively short half-life. The agents used for thyroid imaging include iodine 123 (I123), iodine 131( I131), technetium( Tc 99m) pertechnetate and thallium 201(Tl 201). Scanning is performed 15 minutes after administration of technetium pertechnetate, 4 hours after administration of I123 and 24 to 72 hours after administration of I 131 agents. Scanning is performed 5 to 10 minutes after thallium Tl 201administration. The patient is immobilized in a comfortable position and the scanning tube is run over the neck or other area where functioning tissue is thought to be present. The following information can be obtained from a thyroid scintigram: (1) approximate size and weight of the thyroid gland; (2) its shape (symmetric; one lobe greater than the other; one lobe missing, etc.); (3) distribution of activity (homogeneous; inhomogeneous); and (4) nodules recognition (including their position, size, and degree of activity). A major role of scintigraphy in the evaluation of a thyroid nodule or mass is "hot" (more uptake than the normal thyroid gland), "warm" (some activity but not as much as the normal gland), or "cold" (hypofunctioning). The risk of cancer in a hot nodule is 1 to 4% , in a warm nodule 8 to 10%, and in a cold nodule 15 to 25%. By far the majority (90%) of solitary, hot nodules on scintigraphy are benign in etiology, usually adenomas. A cold nodule is approached more aggressively because of the higher incidence of malignancy. A biopsy or aspiration is often neccessary. Another role of nuclear medicine scintigraphy is to determine whether a patient has a multinodular goiter. A goiter is simply an enlarged thyroid gland, which may be seen with hyperthyroidism or hypothyroidism. The thyroid abnormalities characteristic of Graves' disease result from the action of immunoglobulin of the IgG class on the gland. These antibodies may be directed against components or regions of the plasma membrane that include the receptor for thyroid simulating hormone (TSH) itself. The principal destabilizing factor resulting in autoimmune thyroid disease appears to be an organ specific defect in suppressor T-lymphocytes. Graves' disease is characterized by the association of thyrotoxicosis, diffuse goiter, infiltrative ophthalmopathy and occasionally infiltrative dermopathy. The infiltrative ophthalmopathy follows a course independent from the thyrotoxic component and is not influenced by the treatment. The thyroid scintigram typically shows a symmetrically enlarged gland with homogeneous tracer distribution and a prominent pyramidal lobe. Ectopic thyroid tissue is found in roughly 25% of thyroglossal duct cysts. The incidence of carcinoma within the thyroid tissue of a thyroglossal duct cyst is less than 1%. The lingual thyroid gland represents arrest of migration of the thyroid tissuewithin the tongue, usually in the midline between the circumvallate papillae and the epiglottis. A scintigram alone cannot provide a complete description of the physical structure of the thyroid gland. It only represents the distribution of activity measured over it. Thyroid scintigram 15 THE FUNCTIONAL INVESTIGATION OF THE THYROID THYROID IODINE UPTAKE The radioactive iodine uptake (RAIU) test uses a radioactive tracer to quantify how much tracer the thyroid gland absorbs from the blood. The test can show how much tracer is uptaken by the 131 thyroid gland. I is administrated orally, and the measurements (dosimetry readings) are done at 4 and 24 hours, using a gamma scintillation counter. Conditions to perform a reliable test: the patient is not allowed to eat for 2 hours before the test and to take any antithyroid medicine for 5 to 7 days before the test. The radioactive tracer (11 µCu (microCurrie) is given orally or intravenous. The percentage of thyroidal radioactive iodide uptake (RAIU) is calculated from the counts cumulated per constant time unit, at 2 and 24 hours. The percentage of RAIU 24 hours after the administration of radioiodide is most useful. Normal values for 24-hour RAIU are 5 to 30 percent. Lower normal values are due to the increase in dietary iodine intake following the enrichment of foods, particularly mass produced bread (150 µg of iodine per slice), with this element. The intake of large amounts of iodide (>5 mg/day), mainly from the use of iodine-containing radiologic contrast media, antiseptics, vitamins, and drugs such as amiodarone, suppresses the RAIU values to a level hardly detectable using the usual equipment and doses of the isotope. Depending upon the type of iodine preparation and the period of exposure, depression of RAIU can last for weeks, months, or even years. Even external application of iodide may suppress thyroidal radioiodide uptake. The need to inquire about individual dietary habits and sources of excess iodide intake is obvious. The test does not measure hormone production and release but the avidity of the thyroid gland for iodide and its rate of clearance relative to the kidney. Disease states resulting in excessive production and release of thyroid hormone are most often associated with increased thyroidal RAIU and those causing hormone underproduction with decreased thyroidal RAIU. High or low thyroidal RAIU as a result of low or high dietary iodine intake, respectively, may not be associated with significant changes in thyroid hormone secretion. Examples of thyroidal RAIU curves under various pathological conditions. Note the prolonged uptake in renal disease due to decreased urinary excretion of the isotope and the early decline in thyroidal radioiodide content in some patients with thyrotoxicosis associated with a small but rapidly turning over intrathyroidal iodine pool. Normal range: ~5-30% Increased RAIU Graves Disease Toxic Multinodular Goiter Thyroid Adenoma Decreased RAIU Subacute or Silent Thyroiditis Iodine-Induced 16 THE BASAL METABOLIC RATE (BMR) The basal metabolic rate represents the minimal amount of energy neccesary for the basic vital processes maintenance (respiration, circulation). The principle of determination is represented by the direct relationship between the body oxygen consumption and the amount of heat produced in organism in a given interval of time. For the accurate determination of the BMR , a set of conditions should be accomplished: 1. Rest conditions, avoinding any physical or intelectual effort,: it is also necessary to avoid an intense physical effort 1-2 days before determination, because the biochemical changes associated with physical effort can last few days and can increase the value of BMR. 2. Starvation for 12 hours beforre determination and avoiding of proteins; these nutrients have a special property to release a supplimenatry amount of heat during their metabolization (dynamic specifica activity of proteins). 3. Confort temperature, to avoid the supplimentary expense of energy for termoregulation; an optimal temperature is between 20-22ºC for the dressed subject and 24-26 22ºC for the undressed ones. 4. Avoiding of any emotions, stress, tension, a special relaxing room with walls painted in nonstressfull colours (green, light blue). Steps in BMR determination Body oxygen consumption determination can be measured with Benedict spirometer, which uses a closed system. It consists in a cylinder filled with pure oxygen, immersed at its base in water. The subjects breath pure oxygen from the spirometer for 6 minutes. During this interval, the respiratory movements and their amplitude can be recorded. The expiratory air turns back into the spirometer, so the oxygen isn’t lost. CO2 and water vapors are uptaken by a special substance (sodium carbonate), so the system contains only oxygen. Due to the oxygen consumption, as ascendent slope is recorded , in 6 minutes, by the apparate. The height of this slope is noted with „h”. The determination of the volume of oxygen consumed in 6 min. We use for this determination: O2 caloric coeficient – the amount of energy (in kilocalories) released by 1liter of oxygen, when are metabolised sugars (5,04 cal), proteins (4,48 cal), lipids (4,68 cal);  winch spirogram Pure oxygen water Benedict spirometer The patient inhales pure oxygen from the spirograph cylinder and exhales in the same tube; water vapors and carbon dioxide are removed by a special substance, so in the cylinder will remain only the pure oxyge. As much as oxygen is consumed, the cylinder goes done but the winch, the arrow will draw an ascending slope. The heigh of the graphic = h. h 6 min. Respiratory graph for BMR calculation The subject is connected to apparate and breath pure oxygen for 6 minutes. The recording system shows an ascending graphis, similar to a spirogram. To calculate the oxygen volume consumed in 6 minutes, we have to multiply the h to cylinder surface = 2,85 dm2. VO2 /6 min = 2,85 (dm2) x h (dm) = n dm3 = n liters of oxyge. To calculate oxygen consumption per 24c hours, we have to multiply „n” to 10 and to 24, so: VO2 /24 hours = n x 10 x 24 = liter/24 hours. To calculate the energy consumption, we have to multiply the VO2 /24 hours to oxygen isocaloric coeficient, an average between caloric coeficient of sugars, lipids and proteins , because human food is a balanced one and contain all types of nutrients. The isocaloric coeficient = 4,85 Kcal/l O2 Then energy consumption/24 h = VO2 /24 hours (l) x 4,85 Kcal/l O2. Energy consumption/24 h The BMR = body surface( m2) The obtained result represents the calculated (real) value of BMR in a given person. To interpretate this value, we have to compare it with the standard (theorethical) value of BMR, obtained from tables ( Harris Benedict tables). The theorethical BMR …………………….100% The calculated BMR…………………………..x ΔBMR = 100% + x% = + 10%. The % difference (ΔBMR) between the theorethical BMR and the calculated BMR is normal + 10%. An increased ΔBMR is associated with hyperthyroidism and the decreased ΔBMR with hypothyroidism. 17 THE ORAL GLUCOSE TOLERANCE TEST - OGTT (or provoked hyperglycemia test) consists of the oral administration of a standard amount of glucose followed by blood samples drawning at each hour, for 2 hours. The test appreciates the insulinic response against glucose overload. WHO (World Health Organization) recommended a methodology and interpretation procedure as follows: 3 days before OGTT, patient should follow a standard diet with 150 g sugars, with fats and proteins. The patient should have been fasting for the previous 8-14 hours. Test starts with the drawning of a zero time (baseline) blood sample. The patient is given a glucose solution to drink (pure glucose powder dissolved in water or tea). The standard dose since the late 1970s has been 1.75 grams of glucose / kg of body weight, to a maximum dose of 75 g. It should be drunk within 5 minutes. Prior to 1975 a dose of 100 g was often used. Blood samples are drawn at intervals for measurement of glucose (blood sugar), and insulin levels if neccessary. The intervals and number of samples vary according to the purpose of the test. For simple diabetes screening, the most important sample is the 2 hour sample and the 0 and 2 hour samples may be the only ones collected. INTERPRETATION Glycemia à jeun (uneaten) in normals is bellow 100 mg /dl; A tone hour after glucose ingestion, glycemia increases less then 140 mg/dl in normals; Then decreases, turning back to rest value after 2 hours. The graphic representation consists in two parts: the ascendent slope corresponds with already synthesized insulin release; the second one, descendent slope corresponds with new synthesized and secreted insulin. The abnormalities of one or both of these moments are related with diabetes mellitus risk. If the 1 hour value of glycemia excedes 140 mg/dl, it reflects abnormalities in insulin secretion. If at 2 hour value exceedes 120 mg/dl, it reflects abnormalities in synthesis. A positive OGTT test strongly suggest diabetes mellitus. This is a heterogenous clinical syndrome in which the central feature is a chronic elevation of the blood glucose concentration - this results in a range of pathologies, due to a deficiency of insulin (absolute) or a resistance to insulin (relative). The chronic hyperglycemia is associated with long term tissue damage, especially the blood vessels, nerves, heart, kidneys and eyes. There are two types of diabetes: Type 1 diabetes mellitus appears classically in younger age groups, the onset is acute and insulin is needed for survival - generally present with a history of polyuria, polydipsia, lethargy and weight loss over a period of up to two weeks - many may present with ketoacidosis. In older age groups onset is more insidious - residual beta cell function lessens risk of ketoacidosis at time of presentation. Type2 diabetes mellitus usually occurs in older age groups - especially obese (in 70%) (however, incidence in child is assumed to be increasing due to increased prevalence of childhood obesity). 50% have hypertension and classical signs of thirst, polyuria, nocturia and weight loss are not always present. Often starts with fatigue and malaise.