Application of quantitative salt iodine analysis compared with the standard method.

Laboratory investigation of 50 iodated salt samples (from producers, households, markets etc) were studied at the Research Nuclear Medicine Building, Siriraj Hospital. Two methods for the determination of iodine in salt are herein described. The standard method as recommended by The Programme Against Micronutrient Malnutrition (PAMM) / The Micronutrient Initiative (MI)/ The International Council for Control of Iodine Deficiency Disorders (ICCIDD) was the iodometric titration method. The starch-KI salt iodine quantitative method was developed in our laboratory for validation purposes. This method is high in precision, accuracy, sensitivity as well as specificity. The coefficient of variation (%CV) for intra and inter assay was below 10. Iodine contents as low as 10 ppm, could be detected. The proposed starch-KI method offered some advantages: e.g. not complicated, easier to learn and easier to perform competently, could be applied for spot qualitative test and readily performed outside the laboratory. The results obtained by the starch-KI method correlated well with the standard method (y = 0.98x - 3.22, r = 0.99).

Metastatic follicular carcinoma of thyroid to pericardium.

A 62 year-old man presented with massive pericardial effusion and a thyroid nodule. One thousand ml of serosanguinous pericardial effusion was tapped and the cytology consistent with metastatic papillary carcinoma. Total thyroidectomy was done. The pathological report of the thyroid gland was follicular carcinoma, poorly differentiated with capsular and vascular invasion. The patient received a treatment of 150 mci I-131 without complications. The total body scan after I-131 treatment showed only residual thyroid tissue. There was no demonstrable abnormal uptake in other parts of the body. No significant reaccumulation of pericardial fluid occurred. The diagnosis was follicular carcinoma of the thyroid with pericardial metastasis. The patient was discharged from the hospital with an improved clinical status.

Thyroid scintigraphy in children with hypothyroidism: a five-year experience.

The presence or absence of thyroid glandular tissue demonstrated by thyroid scintigraphy is important for genetic and prognostic counseling and for acceleration of diagnosis in other affected siblings. Technetium-99m-pertechnetate thyroid scintigraphy was performed on 27 children with cretinism at the Division of Nuclear Medicine, Faculty of Medicine Siriraj Hospital during the 5-year period from June 1991. Based on scintigraphic findings, three main groups of thyroid localization were seen. Thirteen (48.1%) were athyrotic while 3 (11.1%) had an ectopic thyroid and 11 (40.8%) had gland in normal position. Perchlorate discharge test was performed in 8 children of the last group and the results were positive indicating an organification defect. Thyroid scintigraphy and perchlorate discharge test provided the useful information for diagnosis, follow-up, and prognosis in children with cretinism.

Circulating levels of T4, T3 and TSH in newborns during the first 7 days of life.

Serum total thyroxine (TT4) and triiodothyroxine (TT3) by radio-immunoassay and thyrotropin (TSH) by immunoradiomebtric assay were measured in the sera of full-term normal newborn infants of both sexes during the first 7 days of life. The results indicated that the mean (+ SE) value of TT4 (11.60 + 0.24 ug/dl) was slightly above our normal adult range while the mean of TT3 (97.48 + 2.84 ng/dl) was within the normal adult range. The levels of serum TSH in the newborns increased markedly at the first day after birth and decreased gradually after 3-7 days of postnatal life with the mean value of 5.02 + 036 nU/l. Thus the normal ranges based on the 95%confidence limits for the results of TT4 (5.00-21.00 ug/dl), TT3 (41.00-195.00 ng/dl) and TSH (0.30-18.00 mU/l) in the neonates were established in order to discriminate euthyroid infant from thyroid disorders of infancy. Serum TT3 and TSH levels of newborns during the first 3 days were found to be significantly higher than those of newborns during 4-7 days (p < 0.005). Moreover, significant sex difference was also obtained in the present study because serum TT4 and TT3 levels of the female infants were statistically higher than those of the male infants, p<0.01 and p<0.05, respectively. In addition, the concentrations of TT4 TT3 and TSH were determined and compared in these newborns following normal labour, caesarean section, gorceps and vaccuum extraction. There was a sharp increase in the mean values of serum TT4 TT3 and utilizing elective caesarean section, while a marked increase in the TSH mean was observed by the methods of forecps extraction and also caesarean section.

Evaluation of the free triiodothyronine index (FT3I) in various thyroid conditions.

Serum total thyroid hormones (TT4 and TT3) have been influenced by alterations in the serum concentration of thyroxine-binding globulin (TTG), and it is necessary to determine the concentrations of free thyroid hormones (FT4 and FT3) which are the biologically active component. However, free T3 index (FT3I) or free thyroxine index (FT4I) measurements are generally accepted clinically so the usefulness and applicability of our FT3I by an in-house method euthyroids, thyroid dysfunction and patients with altered TBG were evaluated. The results indicated that the mean value of serum FT3I in 331 euthyroid subjects was 1.61 + 0.33% (+ SD) with the range of 0.90 – 2.60%. AII the FT3I values in 514 normal pregnancies and 132 chronic renal failure patients were within the normal levels which showed no overlaping results with those of 37 hypothyroids 132 hyperthyroids and 65 pregnant women with hyperthyroidism. Our FT3I gave a more precise index of thyroid status since the data correlated well with clinical observation and the usually routine test of thyroid function. The FT3I has advantages when TBG level are abnormally high or low. Total .T3 (TT3) may be elevated without an elevated TT4 in T3-toxicosis, and thus the FT3I may prevent a misdiagnosis of T3-toxicosis as demonstrated in 61 patients with T3-toxicosis. It is concluded that our FT3I would be very useful in patients with altered TBG or binding capacity and suspected T3-toxicosis.

Can free thyroxine index replace Free thyroxine in thyroid function test.

Serum total thyroxine (TT4) measurement by radioimmunoassy (RIA) has been the most requested test of thyroid function, but high or low values may occur in euthyroid persons as a consequence of alterations in the concentrations or affinities of the serum binding proteins. The free thyroxine index (FT4I) is belive to be an ‘excellent approximation’ of the true concentration of free thyroxine (FT4), which has been shown to define thyroid status in the presence protein abnormality. Our FT4I has been developed by in-house method since 1981. Its value is derived from the ratio of TT4 to T3-uptake that corrects the TT4 for variations in thyroxine-binding proteins. The aim of this study is to compare and evaluate the values of our FT4I and of the Amerlex-M FT4 RIA kit, which is commercially available and is used as a reference method from 662 subjects divided into 5 categories; euthyroid as control, pregnant woman, chronic renal failure (CRF), hyperthyroid and hypothyroid. The results revealed that the values (+SD) of TT and T-uptake in pregnant women and in CRF are deviated from the control, but all the values of FT4I and FT4 in these subjects are within the non-pregnant euthyroid ranges. Our results also indicated that the mean values of FT4I and FT4 in euthyroid, hyperthyroid and hypothyroid differed from one another significantly (p<0.001). Moreover, significant correlations (p<0.01) of the both techniques are obtained in all categories of the subjects, utilizing Spearman’s rank correlation coefficient (rs). Therefore, our FT4I is a reliable substitute for the Amerlex FT4 assay kit in thyroid function test.

The effect of combined oral contraceptives on thyrotoxicosis.

The influence of combined oral contraceptives, namely, ethinyl estradiol (30 µg) and levonorgestrel (150 µg) was studied in nine cases of thyrotoxicosis divided into two groups: one group of htyrotoxic woman treated with propyl thiouracil (PTU) and another untreated group. The latter group of patients were than maintained on both PTU and the combined oral contraceptive pills; some cases were studied for 16-33 months. Before, during and after treatment, all patients were tested and confirmed by clinical examinations and thyroid function tests which were divided into two group: in vivo (24h 131/I uptake and T3-suppression test) and in vivo (total serum thyroxine (TT4), total T3 (TT3), T3 uptake (T3U), free thyroxine index (FTI) and thyrotropin (TSH). The results revealed that the values of TT4, TT3 and FTI were markedly high in the untreated group but these values decreased significantly (P<0.001) and remained within normal ranges after treatment with PTU and the contraceptive pills was initiated. Improved clinical symptoms and sings were also observed. However, the levels of TT4, TT3 and T3 uptake were elevated in the long-term treatments of both groups, but the FTI and TSH values were within normal limits, indicating that the values of FTI as well as TSH gave effective measurements of thyroid activity in evaluating the patients whose total thyroid hormones were abnormal because of altered TBG concentration and binding capacity. Therefore, our finding suggested that the prolonged use of combined oral contraceptive pills dose not interfere with medical treatment of thyrotoxic patients.

Differential diagnosis between neonatal hepatitis and biliary atresia using 99mTc DISIDA scintigraphy.

99mTc DISIDA Scintigrams of intants being investigated for proliged jaundice grom May 1983. to December 1987 were studied in order to determine the accuracy and usefulness of the test in differentiating extrahepatic biliary atresia (EHBA) from neonatal hepatitis. The patients were divided into 2 groups, group A consisting of those done from May 1983 to December 1986 and Group B consisting of those done from January to December 1987. The sensitivity, specificity, accuracy, positive and negative perdictive value of the test in each group were 62, 57, 58, 35, and 90, 77, 83, 75, 91%, respectively. With more experience and improved technique, today 99mTc-DISIDA scintigraphy has become an accurate test foe differentiating EHBA from neonatal hepatitis. When radiotracer is demonstrated in the intestine, EHBA can virtually be excluded. When no bowcl excretion is seen upto 24 hours, EHBA is probable and further invasive procedures are justified.

99mTechnetium - retention.

99mTc-retention is a new index for thyroid function studies. The residual 99mTcO4 content in the thyroid was determined 1 hour after KCIO4 administration. The ratio between the residual and uptake by oral administration, called "99mTechnetium retention," in the hyperthyroid is less than 19.5%. A comparision of diagnostic accuracy between 99mTechnetium retention and other techniques, 99mTechnetium-uptake, RIA serum T3 and T4 was carried out in 200 patients, This yielded overall sensitivity of 93.0%, 91.2%, 82.7%; specificity of 99.3%, 89.1%, 99.2% and 100.0% and accuracy of 97.4%, 89.7%, 94.5%, and 92.3% respectivity. This index is very effective for identifying (1) hyperthyroid and iodine deficiency goiter witout suppression test, (2) relapse and remission of Grave's disease after medical therapy. However such index is not applicable to iodine thyrotoxicosis, thyrotoxicosis factitia, ectopic thyroid production and hyperthyroiditis. Perchlorate (CIO4) ions are not only a competitive inhibitor of TcO4 from the gland. Therefore this technique exposes the least radiation hazard to the gland.