Efficiency of Organic Binding of Trapped Iodide in Sporadic Goiter, Evaluated by the Decrease of Radioiodide Clearance

Summary

The decrease of early thyroid radioiodide clearance was determined in 33 patients with sporadic simple goiter, in 21 normal controls, in 38 hyperthyroid, and 9 hypothyroid patients. The clearance was measured between 5 and 30 min after injection of the tracer, ¹³²I or ¹²³ I, using a single detector system or a gamma camera, respectively. The decrease of clearance was given as the difference between the thyroid radioiodide clearance (ml blood/min) from 5–10 min and 25–30 min post injection.

The relative decrease of clearance was similar in controls and in patients with simple goiter, indicating a normal binding efficiency of trapped iodide in the patients. The median 5–10 min clearance of controls was 85 ml blood/min, and of the patients 125 ml/min, the median decrease of clearance was 26 and 36 ml/min, respectively, i. e. about 30% in both groups; the higher early clearance values correlated significantly with the higher decreases. In the hyperthyroid patients the relative decrease was less pronounced, indicating that the increased iodide trapping in these patients was accompanied by a proportionately greater binding efficiency. In patients with primary hypothyroidism and elevated serum TSH levels the fractional binding of trapped iodide did not differ from normal.

It was concluded that minor degrees of organic binding defects could not be demonstrated in patients with sporadic simple goiter.

Der Schilddrüsenclearanceabfall zwischen 5 und 30 Minuten nach intravenöser Gabe von ¹³²J oder ¹²³J wurde mit einem Einzeldetektorsystem oder mit einer Gammakamera gemessen, und wurde als Differenz zwischen den 5-10 und 25-30-Minuten Clearancewerten angegeben. Die Befunde bei 33 euthyreoten Patienten mit sporadischer, blander Struma wurden mit jenen bei 21 gesunden Personen, 38 hyperthyreoten und 9 hypothyreoten Patienten verglichen.

Der relative Clearanceabfall war bei den Patienten mit blander Struma und bei den gesunden Personen nicht verschieden. Die 5 - 10-Minuten Clearance bei Gesunden war: Mittlere Wert 85 ml Blut/Min, die Differenz 26 ml/Min, bei den Strumapatienten 125 ml/Min, die Differenz 36 ml/Min, d. h. etwa 30 % in den beiden Gruppen. Der Clearanceabfall war höher bei hohen Clearancewerten (r = 0.7). Bei hyperthyreoten Patienten war die Effektivität der organischen Jodbindung höher als bei den euthyreoten Patienten. Bei Hypothyrose mit erhöhtem TSH-Spiegel wurde eine normale fraktionelle Jodidbindung gefunden.

Eine mäßige Herabsetzung der organischen Jodbindung war mit der verwendeten Technik bei blander Struma nicht nachweisbar.

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