The Severity of Symptoms Related to Irritable Bowel Syndrome is a Risk Factor for the Misclassification of Significant Organic Disease.

BACKGROUND AND AIMS: The diagnosis of irritable bowel syndrome (IBS) is based mainly on clinical evaluation. The reported incidence of misclassification of significant organic diseases in previously diagnosed IBS patients differs between studies. The aim of this study was to examine the incidence and risk factors for the misclassification of significant organic disease [colon cancer, inflammatory bowel disease (IBD), Celiac disease, and thyroid dysfunction] in a cohort of young patients with symptoms attributed to IBS. METHODS: In this population-based cohort study, we examined the incidence and risk factors for the diagnosis of a new significant organic diseases in a cohort of 2645 IBS patients. RESULTS: During follow-up, organic disease was diagnosed in 27 subjects (1.03%): IBD in 23, Celiac disease in 2, IBD and Celiac disease in 1, and hypothyroidism in1. The mean interval from the diagnosis of IBS to the diagnosis of an organic disorder was 13.08±8.51 months. Increased symptom severity was the only significant risk factor for the misclassification of an organic disease (hazard ratio, 2.26; 95% confidence interval, 1.01-5.05; P=0.047). The risk ratio for misclassification of organic diseases in moderate to severe IBS was increased by 2.575 (95% confidence interval, 1.10-6.51; P=0.027) as compared with mild IBS. CONCLUSIONS: The incidence of misclassification of major organic disease in IBS patients was low. Increased symptoms severity was the only significant risk factor for the misclassification of organic disorders. Further gastrointestinal evaluation should be considered in patients with moderate to severe symptoms attributed to IBS.

[Blood lipid, glucose and uric acid in people with subclinical hypothyroidism].

OBJECTIVE: To investigate the changes of blood lipid, fasting blood glucose and blood uric acid and its clinical significance in people with subclinical hypothyroidism. METHODS: Body mass index (BMI), thyroid stimulating hormone (TSH), free triiodothyronine (FT3), free tetraiodothyronine (FT4), total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG) and uric acid (UA) were measured and compared in 356 people with subclinical hypothyroidism and 331 health people (controls). RESULTS: Compared to the control group, people with subclinical hypothyroidism had higher levels of BMI, TSH, TC, LDL-C, TG, FBG, UA (P < 0.05) and non-significant decrease of HDL-C (P > 0.05). The level of TSH was positively correlated with TC (r = 0.254), LDL-C (r = 0.110), TG (r = 0.218), BMI (r = 0.119) and FBG (r = 0.210) (P < 0.05). The level of HDL-C was not correlated with TSH (P > 0.05). CONCLUSION: Thyroid dysfunction may have an effect on the metabolism of blood lipid, FBG and UA.

Lingual thyroid with severe hypothyroidism: A case report.

INTRODUCTION: Ectopic thyroid tissue presenting at the base of the tongue, called lingual thyroid, is a clinical rarity. Clinical presentation varies depending upon either the severity of regional symptoms associated with the enlargement of gland size, or the features related to thyroid dysfunction. PATIENT CONCERNS: We reported a case of a 29-year-old female who presented with symptoms of easy fatigue and depression for 3 months. DIAGNOSIS: After a series of diagnostic workup, the lingual thyroid with severe hypothyroidism was diagnosed. INTERVENTION AND OUTCOME: She received conservative treatment with thyroid hormone replacement and the symptoms improved significantly. LESSONS: Lingual thyroid is a rare entity that needs careful diagnostic workup including clinical examination, biochemical tests, imaging methods such as ultrasonography, scintigraphy, computed tomography, magnetic resonance imaging, and fine-needle aspiration cytology to plan the management. Lingual thyroid with hypothyroidism and no neck regional symptoms can be conservatively treated and requires regular follow-up for the prevention of potential risk of malignant transformation.

Using Thypro 39 Scale For Predicting The Quality Of Life In Hypothyroid Patients At Lady Reading Hospital.

BACKGROUND: Thyroid disorders are the second most common of the endocrine diseases. With regards to Hypothyroidism, it has a slow indolent course over the years, before its diagnosis. Most of the patient, on adequate treatment with biochemical euthyroid status, have generalised symptoms that affect their quality of life. Several tools to assess quality of life in thyroid disorders have been validated and recommended for use for those patients in clinical follow ups. ThyPRO 39 is one of a recently developed thyroid-specific quality of life (QoL) questionnaires applicable to patients with benign thyroid disorders (BTD). The purpose of this study was to predict the thyroid-related quality of life (QoL) instrument ThyPRO 39 in patients with Hypothyroidism, who were rendered euthyroid with thyroid replacement therapy prior to the administration of study tool and to assess the internal reliability of this scale in our population. METHODS: A sample of 52 patients undergoing maintenance treatment for Hypothyroidism who visited the outpatient Endocrinology clinics at Lady Reading Hospital was studied. They were interviewed for their baseline demographic details and details on ThyPRO 39 questionnaire were recorded after a written informed consent. The data was entered and analysed using SPSS 25. The Internal reliability of the ThyPRO 39 scale was assessed for multi-item scales using Cronbach's alpha coefficient. RESULTS: The ThyPRO 39 scale demonstrated good response across the whole range of QoL aspects in patients with hypothyroidism. Internal reliability for ThyPRO 39 scale was satisfactory. Cronbach's Alpha in our study was 0.928, which was comparable to the results of other studies. CONCLUSIONS: We suggest implementing this measurement tool as a patient-reported outcome in clinical studies in our indigenous population and further more to utilise it as a screening tool for QoL in clinical management of Hypothyroidism in our routine medical consultations.

Validity of Six Month L-Thyroxine Dose for Differentiation of Transient or Permanent Congenital Hypothyroidism

Objective: The tendency to reduce thyroid stimulating hormone (TSH) referral cut-off values in congenital hypothyroidism (CH) neonatal screening programs has resulted in an increase in the incidence of CH, but also the referral of infants with mild transient elevation of TSH. Therefore, there is a need to develop markers for differentiation of transient elevated TSH and permanent CH as early as safely possible to avoid unnecessary treatment. The aim was to evaluate sixth-month L-thyroxine (LT4) dose as a predictive marker for differentiation of transient elevated TSH and permanent CH. Methods: Data of patients who had been followed after referral from the neonatal screening programme between the year 2010 and 2019 in a tertiary pediatric endocrine centre were examined retrospectively. Results: There were 226 cases referred, of whom 186 (82.3%) had eutopic thyroid gland, and 40 (17.7%) had dysgenetic gland. In patients with a dysgentic gland there was a non-significant tendency to have lower diagnostic free thyroxine concentration but significantly higher TSH compared with those with eutopic gland (p=0.44 and p=0.023, respectively). Patients with thyroid dysgenesis required higher initial and six month LT4 doses compared with those with eutopic glands (p=0.001). Receiver operator curve analysis showed the optimum cut-off value for LT4 at six months for transient vs. permanent CH was 2 µg/kg/day (sensitivity 77% and specificity 55%), regardless of etiology. Similarly, in patients with eutopic glands the optimum cut-off value for LT4 dose at six months for permanent vs. transient patients was 2 µg/kg/day (sensitivity 72% and specificity 54%). Conclusion: Results suggest that LT4 requirement at six months of therapy may be a good marker for predicting transient TSH elevation in patients with eutopic thyroid gland, thus facilitating the decision to halt LT4 therapy.

Recombinant thyrotropin in the diagnosis of congenital hypothyroidism.

CONTEXT: A modern approach to congenital hypothyroidism requires a definitive diagnosis of the underlying mechanisms; this can be achieved within the first weeks of life. When uncertainty persists, treatment is commenced, and the definitive diagnosis of congenital hypothyroidism is deferred to the age of 3 yr. OBJECTIVES: The interruption of thyroid replacement treatment is perceived as risky by parents and physicians. The aim of this pilot study was to test the possibility of a definitive diagnosis during thyroid replacement treatment, using stimulation of thyroid tissue by recombinant human (rh)TSH. SUBJECTS: Eight patients, three boys and five girls, age 5-15 yr (mean, 9.5+/-3.7 yr), with congenital hypothyroidism that had been diagnosed by the neonatal screening program, and having their diagnosis verified between the ages of 3-4 yr, were reevaluated while on thyroid replacement therapy. INTERVENTIONS: Patients received im 0.6 mg/m2 rhTSH on two consecutive days. RESULTS: rhTSH pharmacokinetics, maximal concentration, t1/2, and area under the curve in children were different as compared with adults. In the patients with intact TSH receptors, free T4 levels decreased after the first and the second injection of rhTSH (P=0.0137 and P=0.0149, respectively). All eight children showed identical scintigraphy after rhTSH administration as compared with thyroid replacement withdrawal. CONCLUSIONS: The use of rhTSH is effective for definitive diagnosis of congenital hypothyroidism during thyroid replacement treatment, and no safety issues were encountered.

[Classification of thyroid gland disease on the basis of selenium concentration in serum]. / Klasyfikacja schorzen tarczycy na podstawie stezenia selenu w surowicy krwi.

The aim of this study was to estimate the concentration of total selenium in serum women with thyroid gland disease. Selenium was determined by atomic absorption spectrometry using the hydride generation method (HG-AAS). Research was determined in 94 patients with thyroid gland disease and in 28 healthy controls. Selenium concentration of serum was variously in patients than in control group and patients with different thyroid gland diseases. Concentration in control group was 0.06231 microg/ml, in goitre group--0.05612 microg/ml, in hyperthyroidism--0.07149 microg/ml and in hypothyroidism--0.09088 microg/ml.

Epidemiology of subtypes of hypothyroidism in Denmark.

OBJECTIVE: Studies of hypothyroidism are often based on referred patients, and limited information is available on the incidence rates of subtypes of hypothyroidism in the general population. We therefore studied incidences of subtypes of primary, overt hypothyroidism in a Danish population cohort and compared incidences in two subcohorts with different levels of iodine intake. DESIGN: A prospective population-based study, monitoring a well-defined cohort representative of the Danish population. METHODS: The Danish Investigation of Iodine Intake and Thyroid Diseases registry of hyper- and hypothyroidism was established as part of the monitoring of the iodine fortification of salt in Denmark. A computer-based system linked to laboratory databases identified all patients diagnosed with new, biochemically overt hypothyroidism in populations living in Aalborg (moderate iodine deficiency, n = 311,102) and Copenhagen (mild iodine deficiency, n = 227,632). We subsequently evaluated all identified patients to verify incident thyroid disease, and subclassified hypothyroidism into nosological types. RESULTS: During a 4-year period (2,027,208 person-years) 685 new cases of overt hypothyroidism were diagnosed in the cohort; the incidence rate was 32.8 per 100,000 person-years (standardised to the Danish population). Nosological types of hypothyroidism were: spontaneous (presumably autoimmune) 84.4%, post-partum 4.7%, amiodarone-associated 4.0%, subacute thyroiditis 1.8%, previous radiation or surgery 1.8%, congenital 1.6% and lithium-associated 1.6%. Crude incidence rates were 29.0 around Aalborg and 40.6 in an area of Copenhagen. The higher incidence rate of hypothyroidism in the area with higher iodine intake was caused solely by more cases of spontaneous (presumably autoimmune) hypothyroidism, whereas the incidence of non-spontaneous hypothyroidism (all types combined) was significantly lower in the area with higher iodine intake. CONCLUSION: In a population-based study we observed a higher incidence of hypothyroidism with higher iodine intake. This was due solely to the entity of spontaneous hypothyroidism. The occurrence of overt hypothyroidism was relatively low in Denmark.

Thyroid dysfunction in Down syndrome.

BACKGROUND: Down syndrome is associated with various forms of thyroid dysfunction, hypothyroidism being the most common. The additive effects of both co-morbid conditions lead to further amplification of the clinical problems in these children with Down syndrome. OBJECTIVE: The purpose of this prospective study was to know the prevalence of thyroid dysfunction in Down Syndrome children below the age of 14 years and to correlate the features of Down Syndrome with those of thyroid dysfunction. METHODS: In all 32 Down syndrome children were grouped as euthyroid, compensated and uncompensated hypothyroidism on the basis of their T3, T4 and TSH levels and the features of were compared using the student's t-test. RESULTS: Hypothyroidism was seen in 5 out of 32 cases (15.6%) of which 1 (3.1%) had uncompensated while the other 4 (12.5%) had a compensated hypothyroidism. Hyperthyroidism was not observed in any of the cases. The prevalence of hypothyroidism of 16.7% on the age group 0-1 year could well be a reflection of congenital hypothyroidism while 20% prevalence in the age group 9-12 could imply acquired hypothyroidism. The mean values of the developmental quotient (D.Q.) and the Rao's index in Down syndrome cases with hypothyroidism was 49 5.1 and 0.15 0.06 respectively while that of euthyroid Down syndrome patients were 52 5.54 and 0.17 0.04 respectively ('p' value > 0.05), the differences though obvious yet not statistically significant. CONCLUSION: It thus seems necessary to screen all Down syndrome children for thyroid dysfunction.

Reevaluation of the thyroidal radioactive iodine uptake test, with special reference to reversible primary hypothyroidism with elevated thyroid radioiodine uptake.

The clinical significance of the thyroidal radioactive iodine uptake (RAIU) test was reevaluated in patients with various thyroid disorders. Compared with 262 normal subjects or 194 patients with euthyroid diffuse goiter with normal serum TSH levels, RAIU values were significantly higher in 100 patients with latent primary hypothyroidism (serum TSH, 5-40 mU/L). In 126 patients with overt primary hypothyroidism (serum TSH, greater than 40 mU/L), RAIU values were either extremely high (49 patients with reversible hypothyroidism and 10 patients with postpartum hypothyroidism) or low (67 patients with irreversible hypothyroidism). The increase in RAIU values in latent, or reversible overt hypothyroidism was TSH dependent, and there was a good correlation between RAIU values and serum TSH levels (r = 0.6203; P less than 0.001). In overt primary hypothyroidism, spontaneous recovery of thyroid function during iodide restriction alone occurred in 52 of 53 patients with RAIU values above 35%, in only 7 of 23 patients with RAIU values between 10-35%, and in none of 50 patients with RAIU below 10%. Thus, recovery was predicted by high RAIU values (P less than 0.001; prediction rate, 91.4%). Goiter was found in about 80% of the patients with reversible hypothyroidism, compared with only 34% of the patients with irreversible hypothyroidism. Recovery of thyroid function during iodide restriction also occurred in 71% of the patients with latent hypothyroidism. However, RAIU measurements did not predict the prognosis of patients with latent hypothyroidism. We conclude that iodine-induced reversible hypothyroidism is common in our patient population, and RAIU measurements may be helpful in determining the prognosis of patients with overt primary hypothyroidism.

Primary hypothyroidism manifested in childhood with special reference to various types of reversible hypothyroidism.

The clinical course of 15 patients with overt primary hypothyroidism manifested in childhood were studied. Nine female patients with goitrous hypothyroidism due to chronic thyroiditis showed almost normal height and became euthyroid spontaneously during iodine restriction. The other 6 nongoitrous patients (3M and 3F) (atrophic thyroiditis in 2, lingual goiter in 2 and probable hypoplastic thyroid in 2) showed physical growth retardation and remained irreversibly hypothyroid requiring replacement therapy. In the reversible group, the characteristic findings were high thyroidal radioactive iodine uptake (58 +/- 19%/24 h, N = 8) and positive perchlorate discharge test. Serum nonhormonal iodine levels were high in 4 of 6 patients measured. During the long-term follow-up period of 6 years in 6 patients, 2 patients remained euthyroid with normal growth and regular menstrual cycle and 4 patients became hypothyroid again (after eating seaweed in 1, despite iodine restriction in 2 and after the episode of painless thyroiditis in 1). Transient retardation of growth was observed during the second episode of hypothyroidism. In the irreversible group, one patient with blocking type TSH binding inhibitor immunoglobulin (TBII) became thyrotoxic 4 years later with the decrease in activity of blocking type TBII. These results suggested that reversible recovery of the thyroid function could be expected in patients with juvenile hypothyroidism due to chronic thyroiditis after (1) iodine restriction, (2) improvement of immunological perturbation, or (3) disappearance of blocking type TBII. However, careful follow-up is necessary, because hypothyroidism would recur again with transient retardation of growth in children.

Psychopathological and cognitive features in subclinical hypothyroidism.

1. To evaluate effective and cognitive dysfunctions in subjects with a marginal form of thyroid hypofunction the authors studied a population of female goiter patients, divided in two groups on the basis of thyroid function: euthyroidism and subclinical hypothyroidism (SCH). 2. The SCH patients were treated with levothyroxine (LT4) in order to obtain euthyroidism, as demonstrated by normalization of the hormonal pattern. 3. Both groups were evaluated with a wide range of psychometric tests (Wechsler memory test, scribble test, reaction times) and psychopathological rating scales (Hamilton rating scales for depression and anxiety, brief psychiatric rating scale) at admission and after 3 months. 4. At admission, a significant decrease in logical memory was found in SCH patients; no differences in affectivity ratings were found between the groups. 5. After LT4 treatment, SCH patients showed a significant improvement in some items of memory performance. 6. In conclusion, when interfering factors relating to the perception of disease were excluded by employing euthyroid goiter patients as a comparison group, SCH appeared associated only with memory impairment, while the impairment of affective functions described in previous studies comparing SCH patients with normal controls was not confirmed. A significant improvement of memory skills was induced by LT4 treatment in SCH patients.

Conflict between classifications based on free thyroxine and thyroid stimulating hormone concentrations in thyroxine-treated patients.

The use of free thyroxine assay as the basis for monitoring patients on thyroxine replacement therapy was assessed. Patients with normal free thyroxine levels were divided into sub-groups on the basis of serum TSH levels. Of these, patients with normal TSH levels had higher serum free thyroxine and free 3,5,3'-triiodothyronine concentrations than patients with elevated TSH levels. No significant differences were seen in the level of duration of replacement therapy. Patients were almost equally divided between the high and normal TSH sub-groups. It was concluded that free thyroxine assay had little role to play in the monitoring of these patients.

Lipoprotein(a) and other lipoproteins in hypothyroid patients before and after thyroid replacement therapy.

AIMS: To analyse the influence of thyroid hormones on serum lipoprotein(a) (Lp(a)) concentration and other lipid parameters, and hence potentially on coronary artery disease (CAD) risk. METHODS: Thirty-six patients with hypothyroidism and 165 age-matched control euthyroid subjects were evaluated in a cross- sectional study, determining thyroid function tests and fasting serum lipids and lipoproteins. In a follow-up study for those hypothyroid patients the same determinations were repeated after normalization of thyroid state by levothyroxine (L-T(4)) replacement therapy. Patients needing other treatments were excluded. At baseline, patients with hypothyroidism had significantly higher levels of Lp(a), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apolipoprotein (apo) A-I and apo B, and a higher TC/high-density lipoprotein cholesterol (HDL-C) ratio than control subjects. RESULTS: Severity of the hypothyroid state, expressed by serum thyroid-stimulating hormone, was correlated with serum levels of Lp(a), LDL-C, and TC (r= 0.64, 0.52, 0.49, P= 0.005, P= 0.033, P= 0. 048, respectively). The pretreatment Lp(a) levels were also correlated with those of posttreatment Lp(a)(r= 0.68, P= 0.002). All patients, who presented basal Lp(a) levels higher than 30 mg/dl, showed a decrease in Lp(a) concentrations by L-T(4)therapy, and these normalized in eight cases (22.2%). Euthyroid state gave rise to a significant reduction of serum Lp(a) by 32.3%, of LDL-C by 22. 8%, of TC by 17%, of apo A-I by 9.6%, and of apo B by 9.3%. After L-T(4)therapy, CAD risk, expressed as TC/HDL-C ratio, decreased by 19.9%. CONCLUSIONS: These results show that hypothyroidism is associated not only with elevated serum levels of LDL-C but also with elevated serum Lp(a) concentrations. Lp(a) levels may be at least partially modulated by thyroid hormone-dependent mechanisms, thus increasing the risk of developing premature atherosclerosis in hypothyroid state, that might be reduced by L-T(4)therapy.

Newborn screening for congenital hypothyroidism, Victoria, Australia, 1977-1997. Part 1: The screening programme, demography, baseline perinatal data and diagnostic classification.

Clinical, demographic and laboratory data from infants with congenital hypothyroidism (CH) born in the Australian state of Victoria from the commencement of neonatal screening in mid-1977 until December 1988 are reported. These provide a baseline for a 12-year prospective longitudinal study on physical and neuro-psychological outcome until mid-1997, the subject of a second paper. Infants with CH were detected using a primary TT4 screening test. Demographic data were collected prospectively using a clinical assessment protocol. Nearly all affected infants underwent 99mTc pertechnetate scanning at the initial assessment to determine the underlying aetiology of their hypothyroidism. 704,723 infants were screened and 199 with permanent primary hypothyroidism (one in 3,541) were identified. The most common aetiologies were thyroid ectopia (46%), thyroid aplasia (33%), and 'dyshormonogenesis' (11%). The clinical abnormalities classically described in CH were more evident in infants with aplasia, and the striking female preponderance in infants with thyroid dysplasia (syn. dysgenesis) was confirmed. Other features included increased frequencies of 'dyshormonogenesis' in infants of parents of Middle-Eastern origin and of labour induction in infants with dysplasia. A closed posterior fontanelle was not found in any infant with thyroid aplasia.

Classification of congenital hypothyroidism based on scintigraphy, ultrasonography and the serum thyroglobulin level.

In the present study, infants with congenital hypothyroidism discovered on neonatal mass screening were examined in order to clarify the pathogenesis by means of I-123 or Tc-99m scintigraphy, with and without thyroid ultrasonography and serum thyroglobulin measurement. The patients were divided into two groups: sixteen neonates with hypothyroidism discovered in a neonatal mass screening program performed between 1985 and 1992 (group A), and eleven neonates discovered between 1992 and 1994 (group B). In group A, only I-123 scintigraphy was performed to determine the pathogenesis. Group B was subjected to Tc-99m scintigraphy, thyroid ultrasonography and serum thyroglobulin measurement. The pathogenesis of thirteen patients with congenital hypothyroidism in group A (1985-1992) were as follows; seven patients were diagnosed as having dysorganogenesis, consisting of six with ectopic glands and one with agenesis of the thyroid gland. Six patients were diagnosed as having dyshormonogenesis. All three patients with transient hypothyroidism were diagnosed as having transient dyshormonogenesis. The pathogenesis of eight patients with congenital hypothyroidism in group B (1992-1994) were as follows; one patient of dysorganogenesis with ectopic gland and seven patients of dyshormonogenesis consisting of one patient with iodine transport defect, one patient with iodine transport defect combined with ectopic gland, one patient with dyshormonogenesis combined with dysorganogenesis and four patients with only dyshormonogenesis. All of three patients with transient hypothyroidisms were diagnosed as transient dyshormonogenesis. These results suggest that the examination of thyroid scintigraphy and ultrasonography as well as serum thyroglobulin measurement are useful to clarify the etiology and pathogenesis of congenital hypothyroidism.

Pattern of hypothyroid disorders in Ethio-Swedish Children's Hospital (ESCH).

All children with thyroid disorder attending the endocrinology clinic of the Ethio-Swedish Children's Hospital (ESCH), Addis Ababa in 1996 were included in this study. One hundred twenty six new patients from all over the country were referred to the clinic for thyroid disorder and 31 patients (24%) were found to have hypothyroidism. Seventeen (13%) had congenital hypothyroidism while the rest 14(11.5%) were categorised to have juvenile hypothyroidism. Thyroid dysgenesis is the commonest cause of permanent hypothyroidism. Mental retardation was the accompanied manifestation in all the cases with thyroid agenesis except in two children. Mental retardation being the commonest permanent sequelae in aplastic hypothyroidism is of utmost concern and its prevention is desirable, therefore high index of clinical suspicion with a close observation for early feature of congenital hypothyroidism is warranted for early intervention and in the future nation wide screening for hypothyroidism is recommended.

[Analysis of in vivo and in vitro radioisotopic tests for studying hypothyroidism. Statistical study of parameters coming from routine investigations in normal subjects and hypothyroid patients]. / Analyse des tests radio-isotopiques in vivo et in vitro pour l'étude des hypothyrïdies. Etude statistique de paramètres provenant d'investigations de routine chez des sujets normaux et hypothyroïdiens

This report analyses quantitative data collected during spontaneous examination in normal subjects and in hypothyroid subjects, attempting to determine what figures obtained in this way can provide in the diagnosis of this disease. 125I tests in vitro today play a very important role and suffice der detection provided radio-immunoassay is carried out, whether the latter concerns iodine hormones or the thyreotropic pituitary hormone and provided the diagnosis is not confirmed by one single examination. The 131I kinetic test helps in classification of the hypothyroidism. Naturally, only further tests will permit us to determine certain causes (thyroid scan, Querido's test, TRF test, anionic competition, immunological study, etc.). Chemical estimations of stable iodine (127I) no longer have any place in this routine assessment, except that the total iodine is essential to interpret the kinetics in vivo.

Assessment of dose and time responses to TRH and thyrotropin in healthy dogs.

Changes in total thyroxine (T4 [TT4]), free T4 (FT4) and total tri-iodothyronine (T3 [TT3]) in serum after the intravenous administration of different doses of thyrotropin (TSH) and thyrotropin-releasing hormone (TRH) were measured in six healthy beagles. Significant (P < 0.05) elevations in serum TT4, FT4 and TT3 were observed at each sampling time (two, four, five, six, seven, eight and 10 hours) after administration of 1, 3 or 5 iu (total dose) TSH and peak mean responses were observed six to eight hours after injection. At six hours after injection the mean TT4, FT4 and TT3 levels were approximately 2.6, 3.9, and 1.5 times basal levels, respectively, and there were no significant differences between the three doses of TSH, Significant (P < 0.05) elevations in serum TT4 and FT4 but not TT3 were observed at each sampling time (two, four, five, six, seven and eight hours) after the administration of TRH. Peak mean responses were observed at four hours after injection at which time TT4 and FT4 levels were approximately 1.7 and 1.9 times basal levels, respectively. No significant differences were observed between the four doses of TRH used (100, 200, 300, and 600 micrograms total dose). Concentrations of TT4, FT4 and TT3 were significantly (P < 0.05) higher following the administration of TSH compared with TRH, and the response to TRH showed greater individual variation.