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Abstract. Thyroid volume of 1397 German and 303 Swedish adults were estimated by sonography. Thyroid size of 6–16 year old Germans (n = 619) was determined and compared with findings on palpation. Thyroid volume was more than twice as great in German (21.4 ± 15.6 ml, mean ± sd) than in Swedish adults (10.1 ± 4.9 ml). The echopattern was abnormal in 16% of the Germans and in 3.6% of the Swedes. German children have a thyroid volume ranging from 1.8 ± 0.4 ml at 6 years to 10.8 ± 6.0 ml at 16 years of age. Palpation is by comparison an unreliable method for determining thyroid size. In Germany, the iodine excretion was less in children (n = 619, 39.5 ± 30.5, 34.1 μg I/g creatinine, mean ± sd, median) than in adults (n = 1193, 83.7 ± 94.4, 62.6), (P <0.001) and much lower than that observed in Sweden (adults n = 98, 170.2 ± 93.3, 141.4; 13 year olds n = 113, 172.9 ± 224.1, 124), (P < 0.0001). Serum thyrotropin concentration was significantly higher (P <0.001) in Sweden (n = 62, 1.49 ± 0.82 mU/ml), than in Germany (n = 91, 0.97 ± 0.52 mU/ml), while serum thyroglobulin was increased in Germany (n = 91, 72.6 ± 50.6 μg/l) as compared to Sweden (n = 62, 23.5 ± 17.4), (P <0.0001). These results indicate the goitrogenic effect of iodine deficiency and the continuing need for an effective iodine prophylaxis in the FRG.

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We have studied the relationship between insulin activation of insulin-receptor kinase and insulin stimulation of glucose uptake in isolated rat adipocytes. Glucose uptake was half-maximally or maximally stimulated, respectively, when only 4 % or 14 % of the maximal kinase activity had been reached. To investigate this relationship also under conditions where the insulin effect on activation of receptor kinase was decreased, the adipocytes were expos'ed to 10 ,uM-isoprenaline alone or with 5 jug of adenosine deaminase/ml. An approx. 30 % (isoprenaline) or approx. 50 % (isoprenaline + adenosine deaminase) decrease in the insulin effect on receptor kinase activity was found at insulin concentrations between 0.4 and 20 ng/ml, and this could not be explained by decreased insulin binding. The decreased insulin-effect on kinase activity was closely correlated with a loss of insulin-sensitivity of glucose uptake. Moreover, our data indicate that the relation between receptor kinase activity and glucose uptake (expressed as percentage of maximal uptake) remained unchanged. The following conclusions were drawn. (1) If activation of receptor kinase stimulates glucose uptake, only 14 % of the maximal kinase activity is sufficient for maximal stimulation. (2) Isoprenaline decreases the coupling efficiency between insulin binding and receptor-kinase activation, this being accompanied by a corresponding decrease in sensitivity of glucose uptake. (3) Our data indicate that the signalling for glucose uptake is closely related to receptor-kinase activity, even when the coupling efficiency between insulin binding and kinase activation is altered. They thus support the hypothesis that receptor-kinase activity reflects the signal which originates from the receptor and which is transduced to the glucosetransport system. INTRODUCTIONThe insulin receptor is a transmembrane glycoprotein composed of two a-subunits of 135 kDa and two f-subunits of 95 kDa [1,2]. Insulin binding to the a-subunits causes rapid phosphorylation of tyrosine residues on the fl-subunits [1,3]. The phosphorylation of tyrosine-containing sites on the receptor in turn activates the insulin-receptor kinase toward tyrosine residues of other protein substrates [4][5][6]. Several lines of evidence indicate that autophosphorylation and activation of the insulin receptor as a tyrosine kinase is an important early step necessary for the transduction of many, if not all, of the biological effects of insulin [1,7,8]. A decreased ability of insulin receptors to autophosphorylate or to activate their kinase in response to insulin could therefore cause or contribute to insulin resistance. In fact, a decreased kinase activity of insulin receptors has been found in a variety of situations where the effects of insulin on biological actions are decreased [9][10][11][12][13][14], including type-II diabetes [15][16][17]. For technical reasons it has, however, so far been difficult to relate directly alterations in the coupling between insulin binding and insulin-induced activation o...