Geislajoðmeðferð (I-131) á Íslandi vegna ofstarfsemi skjaldkirtils árin 1985-1991

Abstract

Half a century ago the Icelanders were reported to have the smallest thyroid gland of all nations whose thyroid gland weight was known. This has been thought to be caused by the rich iodine content of the Icelandic food. For that reason and others it is of interest to study some of the thyroid pathology and treatment in Iceland. Treatment of hyperthyroidism with radioiodine (I-131) has become the method of choice amongst adults in Iceland during the last decade. From the beginning of 1985 to the end of October 1991 a total number of 267 hyperthyroid patients were treated with radioiodine at the radioisotope unit of Landspitalinn, the only unit in Iceland involved in that treatment. The radioactivity administered to the patients, the dose of radioactive iodine, was relatively small and aimed at 7000 rads to the thyroid gland. Of 216 patients treated during the years 1985-1990, 41 (19%) needed a second treatment or more due to persisting hyperthyroidism. These patients had significantly larger thyroid glands and higher iodine uptake than the rest of the patients. Two measurements of serum TSH and T4 within 6 months after treatment indicated that about one third of the patients were going from hypothyroid state to euthyroid or hyperthyroid state and vice versa up to that time. These measurements further indicated that about 50% of the patients were hyperthyroid and about 27% hypothyroid at the end of 6 months. A further study by mailed questionnaire to 241 patients (response rate = 75.1%) revealed that about 30% had developed hypothyroidism within 8 months and about 50% within 2 years of treatment. Of the whole group 60% had developed hypothyroidism 7 years after treatment. When groups of patients for each year were studied it was found that there was about 6% average increase of hypothyroidism each year beyond the incidence of the first year. In 7 years from treatment 77% of the patients had developed hypothyroidism. This is a considerably higher incidence than reported in Iceland earlier and is in agreement with observations in other countries showing that the rate of hypothyroidism after radioiodine treatment has been increasing during the last 2 or 3 decades. Irregular pulse rate before treatment was more common (53%) than reported elsewhere. Eye complaints, minor ones mostly, were reported by 22% of the patients. It is concluded that the incidence of hypothyroidism in Iceland after relatively small doses of 1-131 treatment is comparatively high and has increased during the last 20 years for unknown reasons.

Á árunum 1985-1991 voru 267 sjúklingar með ofstarfsemi skjaldkirtils teknir til meðferðar með 13lI (I-131) á Landspítalanum. Geislaskammtar voru tiltölulega litlir og miðuðu að 7000 rad geislun í kirtlinum. Af 216 sjúklingum, sem teknir voru til meðferðar á árunum 1985-1990 þurftu 41 (19%) á endurtekinni meðferð að halda vegna áframhaldandi ofstarfsemi (endurtekin meðferð árið 1991 er ekki talin). Þessir sjúklingar höfðu marktækt stærri kirtil og hærri joðupptöku en hinir sjúklingarnir. Tvennar eftirlitsmælingar á thyroid stimulating hormone (TSH) og thyroxine (T4) í sermi innan sex mánaða frá meðferð bentu til þess að 50% væru áfram með ofstarfsemi og 27% með undirstarfsemi, en breytingar mæligilda hjá sömu sjúklingum bentu til að ekki væru komnar endanlegar tölur. Við frekari könnun með póstsendum spurningalista reyndust um 30% hafa fengið vanstarfsemi í kirtilinn innan átta mánaða og um 50% innan tveggja ára frá meðferð. Sjö árum eftir meðferð voru um 60% allra sjúklinganna með vanstarfandi kirtla. Þegar hópar hvers árs fyrir sig voru skoðaðir, kom í ljós aukning á vanstarfsemi, sem nam að jafnaði um 6% á hverju ári umfram þann hundraðshluta (35-40%), sem fram kom á fyrsta árinu. Sjö árum eftir meðferð voru 77% sjúklinganna með vanstarfandi kirtla. Tíðni á vanstarfsemi skjaldkirtilsins eftir geislameðferð er því há hér á landi miðað við önnur lönd þar sem notaðir hafa verið svipaðir geislaskammtar og hefur hækkað verulega miðað við eldri rannsókn, eins og fundist hefur annars staðar. Oreglulegur púls var algengur (53%) meðal sjúklinga fyrir meðferð.