Scintigraphic imaging of paediatric thyroid dysfunction.

Imaging of thyroid dysfunction is safe and clinically relevant in children. In congenital hypothyroidism (CH), thyroid imaging permits a precise characterization of the aetiology, which is important for genetic counselling and clinical management. CH may be due to thyroid dysgenesis (ectopia, hypoplasia and athyrosis) or occurs in eutopic glands. In the latter, hypothyroidism may be either transient, especially after iodine overload, or due to permanent autosomal recessive dyshormonogenesis. Thyroid scintigraphy (TS) with either 99mTcO4 or 123I will identify ectopic thyroid tissue, which is the commonest cause of CH. However, recent reports favour the use of 123I, which enhances the accuracy of the aetiological classification. In cases of eutopic thyroid, the measurement of 123I uptake before and after perchlorate administration evaluates the organification process. At all ages, colour Doppler ultrasound scanning (CDU) is helpful in assessing thyroid volume, in identifying nodules and in characterizing tissue vascularization. TS and CDU images of most paediatric thyroid dysfunctions are presented.

Decreased uptake of therapeutic doses of iodine-131 after 185-MBq iodine-131 diagnostic imaging for thyroid remnants in differentiated thyroid carcinoma.

We performed a prospective random study to assess possible thyroid stunning by a 185-MBq iodine-131 dose used to diagnose thyroid remnants. Patients with differentiated thyroid carcinoma were included after total or near-total thyroidectomy. They were randomly assigned to two groups. In group 0 (G0, 32 patients), iodine-123 administration only was used to diagnose thyroid remnants and/or metastasis, so that no thyroid stunning by 131I would occur. In group 1 (G1, 19 patients), diagnostic imaging was performed with 123I and 185 MBq 131I. 123I imaging was less sensitive than 131I imaging in identifying thyroid remnants in both groups (94%). Thyroid uptake of 123I was measured in both groups (at 2 h) and was not significantly different between the groups. Patients with thyroid remnants who remained in the study (28/32 in G0, 17/19 in G1) were treated with 370 MBq 131I, 5 weeks after treatment (mean time, range 12-84 days). In 12/17 G1 patients thyroid uptake measurement was repeated immediately before treatment. Uptake was equal to 1.97% +/- 0.71% and significantly lower (P < 0.05) than the previous measurement (3.76% +/- 1.50%). Patients were imaged 7 days after administration of the therapeutic dose and the images were compared with the diagnostic images. In 28/28 G0 patients thyroid remnants were unchanged and clearly seen. In 5/17 G1 patients, however the remnants were hardly identified, although they had been clearly seen at the time of diagnosis. We conclude the following: (1) a diagnostic dose of 185 MBq 131I decreases thyroid uptake for several weeks after administration and can impair immediate subsequent 131I therapy; (2) 123I is slightly less sensitive than 131I in identifying thyroid remnants; and (3) the need to scan for thyroid remnants remains to be confirmed, since only 2/51 patients enrolled in this study were not treated with 131I.

Complete iodide trapping defect in two cases with congenital hypothyroidism: adaptation of thyroid to huge iodide supplementation.

Two cases of congenital defect in iodide trapping mechanism are related. The absence of thyroid and gastric concentration of 99mTcO4 led to the diagnosis. The study of saliva and gastric:serum concentration ratios confirmed the complete defect. The kinetics of radioiodine studied by external detection showed an early simultaneous decay in the thyroid, the stomach and the left ventricle. Thyroid accumulation of 131I, demonstrated by camera imaging, was estimated to be 0.1% at 48 h. It probably originated from simple diffusion. Iodide supplementation was progressively increased to 4.5 g and 10 g day-1 respectively. It resulted in a normalization of all parameters. Huge doses of iodide did not result in any evidence of hyperthyroidism as TSH rose normally after TRH. Intermittent iodide supplementation in one case could not maintain euthyroidism longer than a few weeks. Daily treatment, therefore, seems necessary.

[Congenital hypothyroidism with probable anomaly of thyroid receptiveness to thyrotropin. 2 cases]. / Hypothyroïdie congénitale avec probable anomalie de la réceptivité thyroïdienne à l'hormone thyréotrope. Deux observations.

Congenital hypothyroidism associated with unresponsiveness to thyrotropin (TSH) is a very rare condition. In the two cases reported the thyroid gland was not enlarged and endogenous THS secretion control was normal: the high TSH levels observed during hypothyroidism returned to normal after thyroid hormone replacement therapy and were normally responsive to TRH stimulation. Thyroid iodide clearance was investigated under various conditions of stimulation and inhibition. In hypothyroidism clearance was normal and TSH levels very high. During replacement therapy clearance seemed to be inversely correlated to levels of circulating thyroid hormones; it was almost nil in euthyroidism. Whatever the level of circulating hormones, clearance was not reactivated by exogenous TSH. In one patient in euthyroidism clearance, which was virtually zero, was unmodified after butyric AMPc stimulation, which suggests that the anomaly lies below the AMPc stage.

Pulmonary metastases in differentiated thyroid carcinoma. Study of 58 cases with implications for the primary tumor treatment.

Fifty-eight cases of pulmonary metastases (PM) from 831 cases of differentiated thyroid carcinoma (DTC) were studied. PM were found in about 10% of follicular and 5% of papillary tumors. 131I uptake was found in 55% of the cases, irrespective of histology. Twenty-one patients were treated by 131I only and 12 were cured. Micronodular metastases, 92% papillary, with 86% positive 131I uptake and 77% 8-year survival rate, are the most favorable forms. In others the influence of PM size/age, uptake, delay of appearance, presence of cervical or mediastinal lymph nodes is discussed. Occurrence of late PM according to treatment of the primary tumor was 1.3% thyroidectomy + 131I; 3% thyroidectomy; 5% partial thyroidectomy + 131I; 11% partial thyroidectomy only. Thus prevention in DTC of severe PM (28% 8-year survival rate) can best be achieved by complete thyroidectomy + 131I ablation dose.

[Thyrotoxicosis, then hypothyroidism caused by iodine overload (amiodarone) associated with neuropathy. Failure of plasma exchange]. / Thyréotoxicose, puis hypothyroïdie par surcharge iodée (amiodarone) associées à une neuropathie. Echec des échanges plasmatiques.

A 54-year-old woman, with no previously documented thyroid disease, treated with amiodarone (200 mg/day, five days a week for 33 months) for paroxysmal tachyarrhythmia complicating mitral stenosis, suddenly developed extremely severe thyrotoxicosis. After therapeutic failures with carbimazole and propylthyrouracil (PTU) associated with beta-blockers, she was transferred to intensive care for plasma exchange (PE). Two PE were performed, temporarily aggravating the cardiovascular status of the patient, with no secondary improvement. The quantity of T3 removed was very small, about 1,000 ng per exchange. On the 14th day PTU had to be discontinued (toxic thrombopenia) and only symptomatic treatment was maintained (assisted ventilation, digitalis, hyperalimentation). In the 4th month, while the patient had a high total serum iodine, hypothyroidism developed due to partial block of the organification of the iodine with high TSH and fixation; this state also lasted 4 months. Spontaneous recovery was observed after 8 months. In addition a severe peripheral neuropathy was observed during the hyperthyroid phase confirmed by electromyography, distinct from the signs of thyrotoxic myopathy. This gradually regressed over 7 months and may be attributed to amiodarone therapy. The association of these two successive types of thyroid disorder due to amiodarone is an exceptionally rare phenomenon. Severe thyrotoxicosis generally requires long-term symptomatic therapy, its natural course being towards spontaneous regression. PE are ineffective on the circulating hormonal levels and were dangerous because of the underlying cardiac disease. The development of hypothyroidism at the 4th month is explained by the persistent iodine overload, and therefore prolonged surveillance after withdrawal of therapy is advised. The neurological complication of amiodarone was quite distinct from the hyperthyroid myopathy.

[Adrenocortical scintigraphy with 131I-19-iodocholesterol. Indications and results in 66 cases of hypercortisolism and hyperaldosteronism (author's transl)]. / Scintigraphie cortico-surrénalienne au 131I-19-iodocholestérol. Indications et résultats dans 66 observations d'hypercortisolisme et d'hyperaldostéronisme.

Scintigraphy was used in 66 patients with biochemically demonstrated hyperactivity of the adrenal cortex in order to determine the nature and site of the lesions. In cases of hypercortisolism, uptake was bilateral in 12 patients with Cushing's disease, unilateral in 7 patients with malignant or non-malignant tumours, and absent in 3 cases of large malignant tumours. In cases of hyperaldosteronism, scintigraphy performed during dexamethasone-induced ACTH suppression showed distinctly asymmetrical uptake in 13 patients with Conn's adenoma (confirmed by surgery as being on the good uptake side in 10 patients), symmetrical in 20 patients with biochemical findings indicating bilaterality, and intermediate in 9 patients. There was no false positive diagnosis of tumour. Scintigraphy appears to be of considerable value for locating adrenocortical lesions, especially small tumours.

[The thyroid gland of the newborn infant and postnatal iodine overload]. / Thyroïde du nouveau-né et surcharge en iode après la naissance.

Severe iodine-induced hypothyroidism was recently diagnosed in several neonates raising the responsibility of the iodine antiseptic agents routinely used in these patients. Postnatal iodine overload due to cutaneous application of these agents (povidone iodine and fluorescinated alcoholic-iodine solution) was studied in 5 patients. Thyroid function studies were performed in iodine-overload neonates and in control neonates with comparable gestional age. Results indicated strong evidence of cutaneous absorption of iodine from the antiseptic agents used, leading to hypothyroidism in 12 of them. The frequency and the severity of thyroid dysfunction was closely related to the degree of prematurity. Full recovery was observed in all cases after withdrawal of the iodine-containing agents. It is therefore recommended to avoid any postnatal use of iodine preparations in neonates, mainly in preterm infants, and to use iodine antiseptic agents with great caution, when necessary during the neonatal period.

[Diagnostic of left-to-right shunt by isotopic angiocardiography (author's transl)]. / Shunts gauche-droite: diagnostic par angiocardiographie isotopique.

Isotopic angiocardiography was performed in 60 patients with proven congenital left-to-right shunt. A 99mTc labeled bolus was injected in a peripheral vein, and the first passage in the heart cavities was studied. Time-activity curves of the cardiac chambers were analysed, using a scintillation camera and a data processing system. In our study, we were able to confirm the presence of the shunt in 77% of the cases in which the radioactive bolus arrived well grouped in the vena cava. Quantitative results however remain imprecise. Isotopic angiocardiography indications are compared to radiologic angiocardiography and to right heart catheterism indications. Use of this non invasive technique could render more aggressive examinations unnecessary.

[Quantitative aspects of iodine metabolism in one case of congenital iodotyrosine deiodinase defect (author's transl)]. / Aspects quantitatifs de la cinétique de l'iode dans un défaut d'iodotyrosine desiodase.

In a 27 years old patient an iodotyrosine deiodinase defect was responsible for a profound hypothyroidism (T4-RIA: indetectable -- TSH: 190 microU/ml) associated with a large goiter (about 300 g). MIT and DIT secretions were measured from the urinary cumulative specific activities, and the molar MIT/DIT ratio was 2.2. The thyroidal iodine exchangeable pool was as low as 177 micrograms. In two comparable patients rendered euthyroid by Lipodol injection, total thyroidal 127I pool was around 40 mg and the MIT/DIT ratio was degraded to 7 suggesting a mild biosynthetic defect by iodine excess.

[Neonatal hypothyroidism induced by the ingestion of potassium iodide during pregnancy (author's transl)]. / Hypothyroïdie néo-natale induite par la prise d'iodure de potassium durant la grossesse.

This concerns a case of an infant born with goiter and hypothyroidism whose mother had taken potassium iodide during pregnancy in the form of a respiratory eupneic syrup. Laboratory tests revealed the etiology of the goiter by demonstrating that it concerned a transitory, acquired hormone production disturbance. The tests gave an indication of the course of the condition, leading to substitute hormone therapy being stopped after six weeks. The euthyroidism was then checked on two occastions.

[Hyperthyroidism induced by iodine in an apparently normal thyroid gland. A new iatrogenic disease]. / L'hyperthyroïdie induite par l'iode sur une glande thyroïde apparemment normale. Une pathologie iatrogène nouvelle

Iodine-induced thyrotoxicosis was reported to occur in patients with previously altered thyroid gland. Evidence is presented here from 23 cases that iodine-induced thyrotoxicosis may also occur in patients with no prior thyroid desorder and is characterized by: a) an almost undetectable 131I uptake, wich can be activated by TSH; b) a spontaneous improvement within a few weeks or months after withdrawing the high intake of iodine; c) the absence of any detectable thyroid abnormality after recovery.