La fréquence de l’hypothyroïdie au décours de l’irradiation de la tête et du cou est estimée entre 10 et 45 % après radiothérapie seule et entre 40 et 67 % après radiothérapie associée à une ...chirurgie thyroïdienne. Elle est infraclinique dans 60 % des cas. Notre étude a porté sur 15 cas d’hypothyroïdie après radiothérapie externe colligés sur une période de huit ans (1991–1999). Une irradiation de la région cervicale, cérébrale et thoracique avait été indiquée pour différents types de cancers dont le plus fréquent était le carcinome épidermoïde du larynx (sept cas) . L’irradiation a été réalisée avec un appareil de télécobalthérapie à raison de cinq fractions de 2 Gy par semaine. L’hypothyroïdie était infraclinique et découverte lors d’un bilan systématique dans neuf cas et cliniquement évidente dans les six cas restants. L’hypothyroïdie est apparue à partir d’une dose d’irradiation moyenne de 50 Gy (extrêmes : 30–65 Gy). La durée moyenne de l’irradiation était de sept semaines et le délai moyen d’apparition de l’hypothyroïdie est de 22 mois. Le traitement substitutif a été instauré dans tous les cas avec obtention d’une euthyroïdie clinique et biologique dans tous les cas. Devant ce risque d’hypothyroïdie, une surveillance régulière de la fonction thyroïdienne est nécessaire après irradiation de la tête et du cou.
Hypothyroidism frequency is estimated to be between 10 and 45% after radiotherapy alone, and 40 to 67% after radiotherapy associated with thyroidectomy. This hypothyroidism is infraclinical in 60% of the cases. Our study concerned 15 cases of hypothyroidism after external radiotherapy delivered between and 1991 and 1999. An irradiation of the cervical, cerebral and thorax regions was indicated for different types of cancers. Larynx carcinoma epidermoid was the most frequent cancer (seven cases); the radiation treatment used cobalt 60 with conventional fractionation, i.e., 2 Gy per treatment, five treatments a week. In nine cases, the hypothyroidism was discovered during a systematic examination; it was clinically evident in the six remaining cases. Hypothyroidism appeared after an irradiation dose average of 50 Gy (extremes 30–65 Gy). The average duration of the irradiation was about 7 weeks and the hypothyroidism appeared in a mean 22 months. In all cases, the substituting treatment was initiated with a favorable progression. Faced with the risk of hypothyroidism, it is necessary to check patients who have undergone external irradiation of the neck.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Autoimmune thyroid disease (AITD), including Graves’ disease (GD), Hashimoto thyroiditis (HT), and primary idiopathic myxedema, is caused by multiple genetic and environmental factors. Genes involved ...in immune response and/or thyroid physiology appear to influence susceptibility to disease. The PDS gene (7q31), responsible for Pendred syndrome (congenital sensorineural hearing loss and goiter), encodes a transmembrane protein known as pendrin. Pendrin is an apical porter of iodide in the thyroid. To evaluate the contribution of PDS gene in the genetic susceptibility of AITD, we examined four microsatellite markers in the gene region. Two hundred thirty-three unrelated patients (GD,141; HT, 54; primary idiopathic myxedema, 38), 15 multiplex AITD families (104 individuals/46 patients) and 154 normal controls were genotyped. Analysis of case-control data showed a significant association of D7S496 and D7S2459 with GD (P = 10−3) and HT (P = 1.07 10−24), respectively. The family-based association test showed significant association and linkage between AITDs and alleles 121 bp of D7S496 and 173 bp of D7S501. Results obtained by transmission disequilibrium test are in good agreement with those obtained by the family-based association test. Indeed, evidence for linkage and association of allele 121 bp of D7S496 with AITD was confirmed (P = 0.0114). Multipoint nonparametric linkage analysis using MERLIN showed intriguing evidence for linkage with marker D7S496 in families with only GD patients Z = 2.12, LOD = 0.81, P = 0.026. Single-point and multipoint parametric LOD score linkage analysis was also performed. Again, the highest multipoint parametric LOD score was found for marker D7S496 (LOD = 1.23; P = 0.0086) in families segregating for GD under a dominant model. This work suggests that the PDS gene should be considered a new susceptibility gene to AITDs with varying contributions in each pathology.
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