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Loss of Pertechnetate from the Human Thyroid

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Loss of Pertechnetate from the Human Thyroid LOSS OF PERTECHNETATE FROM THE HUMAN THYROID J. G. Shimmins Regional Dept. of Clinical Physics and Bioengineering, Western Regional Hospital Board, Glasgow, Scotland R. McG. Harden and W. D. Alexander University Department of Medicine, Western Infirmary, Glasgow, Scotland The pertechnetate ion, like the iodide ion, is Magnascanner V (3,6) were started immediately trapped by the thyroid gland (1 ). Several authors after injection and were continued for 45 mm when have claimed that pertechnetate is not bound in the five scans had normally been completed. The scan thyroid (2) and that the gland behaves as a single speed was 100 cm/sec, and the line spacing was compartment (3) . However, the finding of organic 1 cm. Venous blood samples were taken at 2, 8, 15, binding of 9DmTcin rats (4,5) raises the question 30 and 45 mm. One gram perchlorate was given of whether some such binding may not occur in man. orally as a crushed powder in nine subjects 50 mm In this study we have investigated the binding of after the intravenous administration of pertechne pertechnetate in the human gland by measuring the tate. The same amount was given orally to the re rate of pertechnetate discharge from it after per maining four 3 hr after intravenous administra chlorate administration and have compared this rate tion of pertechnetate. Scans were carried out for an of discharge with the normal loss rate of pertechne additional 45 min after perchlorate administration, tate from the thyroid (3). If pertechnetate is Un and blood samples were taken at 2, 8, 15 and 45 bound, it should be possible to discharge it from min. The ODmTcO— activity in blood and in the the thyroid with perchlorate. thyroid was calculated from the time of injection to 45 mm after perchlorate administration. MATERIAL AND METHODS Thirteen patients were studied. Eleven were euthy roid and two were hyperthyroid. One millicurie of Received Nov. 8, 1968; original accepted April 29, 1969. OomTc4abeledpertechnetate was given by intravenous For reprints contact: I. Shimmins, Regional Dept. of Clinical Physics and Bioengineering, Western Regional Hos. injection. Scans of the thyroid region using a Picker pital Board, 11 W. Graham St., Glasgow, C.4, Scotland. TABLE 1. VALUES FOUND FROM UPTAKE CURVE ratePatient Unidirectional20.minIntrathyroidallntrathyroidal turnover Diagnosis clearance (mI/mm)uptake (%)space (ml)(uptake, min1) Euthyroid 4.9 0.7 52 0.076 M Euthyroid 33.0 5.0 440 0.075 BG Euthyroid 35.2 3.4 280 0.080 HY Hyperthyroid 320 34.2 6550 0.049 FMcK Euthyroid 14.0 1.5 191 0.073 MMcK Euthyroid 8.2 0.5 76 0.108 K Euthyroid 27.8 2.3 264 0.105 A Euthyroid 1.8 0.2 58 0.031 McMA Hyperthyroid 248.0 17.5 3350 0.074 McF Euthyroid 22.0 1.6 177 0.124 HN Euthyroid 36.3 6.3 116 0.031 McMl Euthyroid 22.9 3.8 520 0.044 BA Euthyroid 33.0 5.5 850 0.039 Mean 0.070 SEM 0.0083 Volume 10, Number 10 637 SHIMMINS, HARDEN AND ALEXANDER The thyroid uptake after perchiorate administra tion was plotted on a semilogarithmic scale against time after perchiorate administration. The best fit line to this plot gave the intrathyroidal turnover rate during perchiorate discharge. RESULTS The values found for unidirectional clearance, 20- mm uptake, intrathyroidal space and intrathyroidal turnover rate are shown in Table 1. These values are found from the early part of the uptake curve. The 20-min uptake, unidirectional clearance and intra thyroidal space are all considerably higher in the A o 16 32 4B 64 80 96 two hyperthyroid subjects and are considered sepa @ TIME INJECTION (mm) rately. The intrathyroidal turnover rate is not de pendent on thyroid activity (3) , and we have there @ PLASMA YcO4 ,@DOSE/mi fore calculated the mean value (0.070 min 1) for O•017 PERCHLORATE DISCHARGE all the patients measured during the uptake phase. Table 2 shows the intrathyroidal turnover rate meas ured during discharge with perchlorate at two time intervals after isotope administration. The mean in :‘: \\@ trathyroidal turnover rate was 0.089 min'. The two measurements of KTB are also expressed as a ratio, the uptake phase measurement being divided into the discharge phase measurement for each pa 0•005 tient. The mean value found for the ratio KTB(dis charge)/KTB(uptake) was 1.43. 0401 Typical thyroid uptake and discharge patterns for .,III, @1@@ °@‘°TcO4and the corresponding blood activity curve B 0 16 32 48 64 80 96 are shown in Fig. 1. The discharge occurs very rap TIME (Mi,s( idly after the administration of potassium perchlo FIG. 1. A showsthyroiduptakeof pertechnetateanditsdis. rate. Some, but not all, plasma-activity curves showed charge with perchlorate for patient BA. Experimental paints are shown. B shows corresponding plasma pertechnetate activity for patient BA. In this case rise in activity is found after perchlorate administration. TABLE2. INTRATHYROIDALTURNOVERRATE MEASUREDDURING DISCHARGEWITH CALCULATIONS PERCHLORATE The unidirectional clearance, intrathyroidal loss Intrathyroidalturnover rate and intrathyroidal space were calculated on the rateTime uptake part of the experiment by drawing tangents ofIntrathyroidal(discharge)perchlorateturnover rateIntrathyroidaldischarge(discharge,turnover to the uptake plot (3) . The gradient of the tangent ratePatient to the uptake and the uptake were divided by the (mm)min1)(uptake) serum OOmTcactivity at several points along these 180 0.050 0.66 curves. These parameters were then plotted. M 131 0.083 1.11 80 184 0.119 1.49 MY 194 0.077 1.57 @99mTcthyroid uptake FMcK 48 0.063 0.86 . dt —Unidirectional MMcK 49 0.139 1.29 @ i.e. DOmTcplasma clearance K 50 0.114 1.09 A 50 0.073 2.35 KTh @°‘°Tcthyroid uptake McMA 49 0.106 1.43 — x V9mTc plasma McF 50 0.120 0.97 HN 49 0.067 2.16 KTB = Loss rate of @@mTcfrom thyroid. McMI 48 0.080 1.82 BA 53 0.068 1.74 The unidirectional clearance and the intrathyroidal Mean 0.089 Mean 1.43 turnover rate (KTB) were found by drawing the best SEM 0.0075 SEM 0.14 line through this plot. 638 JOURNAL OF NUCLEAR MEDICINE PERTECHNETATE LOSS FROM THYROID binding was found more than 12 hr after isotope TABLE 3. REMAINING @9°'TcACTIVITY 45 MIN administration. As almost all diagnostic tests with AFTER PERCHLORATEDISCHARGE technetium are carried out within 3 hr of isotope uptakeLowestremainingUptakeuptakeafterbeforemeas.% administration, it is safe to assume that for routine purposes no significant amounts of technetium are bound. after45-mmPatient dischargedischargedischarge In a previous communication we have shown that up to 360 mm after injection, the thyroid behaves 0.63 0.061 9.68 M 2.2 0.19 8.63 as a single pool for technetium concentration (3). BG 2.15 0.13 6.04 On this basis we have calculated the unidirectional MY 29.0 2.4 8.27 clearance and intrathyroidal loss rate of pertechne FMcK 1.1 0.11 10.0 MMcK 0.48 0.03 6.25 tate. The administration of perchlorate changes this K 2.4 0.11 4.58 model. The exponential manner of the pertechnetate A 0.22 0.02 9.09 discharge confirms the fact that perchlorate blocks McMA 17.5 0.051 0.29 McF 1.7 0.016 0.94 the trapping of technetium and eliminates the uni MN 7.2 0.62 8.61 McMI 3.6 0.35 9.72 BA 6.5 0.64 9.85 THYROID @mTcO4 Mean 7% UPTAKE °#@ 10 8 an increase in activity after discharge of TcO4 from the thyroid. Figure 2 A and B shows the cx KTR sIRS? mIn@ ponential fall of thyroid uptake after perchlorate discharge. In every case the fall in thyroid uptake after discharge could reasonably be described as a single exponential. Figure 2 B shows the only pa tient for whom it might be thought that a second exponential might exist. In every case 90% of the DDmTc activity was discharged within 45 min of perchlorate administration. Table 3 shows the re maining ODmTcactivity 45 mm after perchlorate 04 discharge. It can be seen that on the average only A 5 10 20 30 40 50 7% of the activity is left after 45 mm of discharge. TIME aft.. PERCHLORATEDISCHARGE mi.) In every case the uptake is still falling, and this value of 7% must be considered as the greatest pos sible bound fraction of DDmTc.Figure 3 shows the relationship between the uptake-phase measurement of KTB and the discharge KTh measurement. There is a linear relationship between these two measure ments of KTB (r = 0.72). KTS .0177mm1 DISCUSSION Several authors have described the organic bind ing of DDmTcO—in the thyroid glands of mice and rats. In man, however, currently available evidence x x x suggests that at early time intervals such binding does x not occur (2,3) . The discharge of technetium from the gland by perchlorate which we have shown is A further evidence against binding in man up to 3 hr 10 20 30 40 after isotope administration. Over this period, less B TIME oft., PERCHLORATE DISCHARGE ( mm) than 10% of the thyroid technetium is bound. The possibility of technetium binding at later times after FIG. 2. In A thyroidpertechnetatefallsexponentiallyfor pa. isotope administration, however, is not excluded; tient MN after perchlorate administration. In B patient MY shows possible second exponential in thyroid discharge. Nevertheless, indeed in the animal studies reported evidence for 90% of pertechnetate is discharged by 45 mm after perchlorate. Volume 10, Number 10 639 SHIMMINS, HARDEN AND ALEXANDER SUMMARY By using a simple method of quantitating scinti x scans of OOmTcO4_in the thyroid, we have shown y.0lSx + 0044 that this ion is not significantly bound up to 3 hr after x administration.
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