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... 8 • 25 Other radioisotopes of iodine are less suitable because of inappropriate half-lives or photon energies, or an excessive absorbed radiation dose from particulate emissions. 8 · 15 • 25 Like stable iodine (1 27 1), radioactive iodine is actively concentrated or trapped by the thyroid gland, where it is incorporated into tyrosine residues of thyroglobulin in a process called organification. 8 • 15 • 25 Pertechnetate ion, with a size and charge similar to that of iodine, is also trapped by the thyroid gland. ...
... Hyperfunctional tumors causing hyperthyroidism appear as moderate to extensive areas of increased, usually uniform, tracer uptake (Fig. 9).  In some dogs, areas of normal to decreased tracer uptake are interspersed with hyperfunctioning areas. The intensity of the thyroid image is greater than that of the salivary glands on pertechnetate scans. ...
... (From Peterson ME, Becker DV: Radionuclide thyroid imaging in 135 cats with hyperthyroidism. Vet Radiol 25: 1984; with permission.) ...
Nuclear medicine may have both diagnostic and therapeutic utility during the evaluation and management of thyroid disease. This article will focus on the use of radionuclide scintigraphy and radioactive iodine therapy in the diagnosis and treatment of thyroid disease in the dog and cat.
... In that study, rhTSH (100 mg IV, administered 24 h or 48 h before 123 I) also did not cause a significant change in thyroid RAIU. Earlier reports have suggested the potential of exogenous TSH to increase thyroid RAIU in dogs [26,27,28]. However, in these studies the effect of TSH stimulation on thyroid 131 I uptake was described in a small number of healthy and hypophysectomized dogs and no statistical analysis was performed. ...
... The significantly different effect of rhTSH on thyroid RAIU between euthyroid and hyperthyroid patients was an interesting finding. In a study of 55 dogs with thyroid tumors, dogs with evidence of autonomous hyperfunction of the goiter had an increased thyroidal iodine turn-over . It is possible that a positive effect of rhTSH on tumor RAIU occurs sooner in hyperthyroid patients and was, therefore, not observed with our protocol (RAIU determination 8 h and 24 h after 123 I injection). ...
In humans, recombinant human thyrotropin (rhTSH) enhances radioactive iodine uptake (RAIU) in patients with differentiated thyroid cancer. No studies have been performed in veterinary medicine to optimize radioiodine treatment of thyroid cancer. The aim of this study was to evaluate the effect of rhTSH on the uptake of radioiodine-123 ((123)I) in dogs with thyroid tumors. Nine dogs with thyroid neoplasia were included in this prospective cross-over study. The dogs were divided in 2 groups. In one group, (123)I was administered for a baseline RAIU determination in week 1. In week 2 (after a washout period of 2 weeks), these dogs received rhTSH (100 μg IV) 24 h before (123)I injection. In the other group the order of the protocol was reversed. For each scan, the dogs received 37 MBq (1 mCi) of (123)I intravenously (IV) and planar scintigraphy was performed after 8 and 24 h for tumor RAIU calculation. Overall, rhTSH administration caused no statistically significant change on thyroid tumor RAIU at 8 h (p = 0.89) or at 24 h (p = 0.98). A significant positive correlation was found between the effect of rhTSH on tumor 8h-RAIU and rhTSH serum concentrations at 6 h (τ = 0.68; p = 0.03), at 12 h (τ = 0.68; p = 0.03) and at 24 h (τ = 0.78; p = 0.02) after rhTSH injection. This study suggests that IV administration of 100 μg rhTSH 24 h before (123)I has an inconsistent effect on thyroid tumor RAIU. Further studies are necessary to determine the best protocol of rhTSH administration to optimize thyroid tumor RAIU.
... These findings raise important issues regarding the optimal dosage, timing, and route of rhTSH administration when the goal is to increase thyroid RAIU, as earlier studies have shown that bTSH increases thyroid RAIU in healthy dogs and in dogs with secondary hypothyroidism.  Additional research therefore is warranted. ...
Recombinant human thyrotropin (rhTSH) was developed after bovine thyrotropin (bTSH) was no longer commercially available. It was approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMEA) as an aid to diagnostic follow-up of differentiated thyroid carcinoma in humans and for thyroid remnant ablation with radioiodine. In addition, rhTSH is used in human medicine to evaluate thyroid reserve capacity and to enhance radioiodine uptake in patients with metastatic thyroid cancer and multinodular goiter. Likewise, rhTSH has been used in veterinary medicine over the last decade. The most important veterinary use of rhTSH is thyroidal functional reserve testing for the diagnosis of canine hypothyroidism. Recent pilot studies performed at Ghent University in Belgium have investigated the use of rhTSH to optimize radioiodine treatment of canine thyroid carcinoma and feline hyperthyroidism. Radioiodine treatment optimization may allow a decreased therapeutic dosage of radioiodine and thus may improve radioprotection. This review outlines the current uses of rhTSH in human and veterinary medicine, emphasizing research performed in dogs and cats, as well as potential future applications.
... In most euthyroid humans (13) and dogs (1) maximal uptake values are reached between 24 and 48 hours, which was also the case in our healthy cats. In hyperthyroid humans (13) and dogs (7,11) the combination of a high thyroidal clearance and a rapid thyroidal turnover of iodine give a characteristic appearance to the thyroid radioiodine uptake curve. There is a rapid initial rise, followed by a decline due to the discharge of iodothyronines. ...
Thyroidal radioiodine uptake was measured in 10 healthy domestic cats and in 20 hyperthyroid cats. Compared with those in the healthy cats, the uptake curves in the hyperthyroid cats were characterised by elevated uptake and rapid thyroidal iodine turnover. For diagnostic purpose uptake measurements at 4 hours after administration of the tracer were found to be preferable to measurements at 24 hours or later.
Het aantal publicaties over het gebruik van medische beeldvorming bij schildklieraandoeningen bij de hond is beperkt. Beschikbare studies rapporteren enkel het gebruik van echografie (US) en planaire scintigrafie in gevallen van schildkliertumoren. De toegenomen beschikbaarheid van andere beeldvorming- technieken, zoals Computed Tomography (CT) en Magnetic Resonance Imaging (MRI), maakt deze potentieel waardevol als bijkomstige testen in de soms moeilijke diagnose en bij het opstellen van een geschikt behandelingsprotocol voor schildklieraandoeningen bij de hond. Als voorbereidende studie werd de herhaalbaarheid van US metingen bepaald. Van verschillende metingen, gemeten door verschillende onderzoekers, hadden de hoogte- en volumemetingen de grootste herhaalbaarheid. De variatie binnen de verschillende onderzoekers was kleiner dan tussen de verschillende onderzoekers. De volgende kenmerken werden echografisch waargenomen in een populatie hypothyroIde honden: hypoechogeen en heterogeen parenchym, onregelmatige aflijning van het kapsel, ronde vorm van de schildklierlob op dwarsdoorsnede en verkleind schildklier volume. De vijf parameters gecombineerd, resulteerde in een sensitiviteit van 94% in de detectie van hypothyroidie. Een continue afname in volume van de schilkier werd opgemerkt na opstarten van de behandeling. US is een gevoelige en snelle test voor het opsporen van hypothyroidie bij de hond. Een volgend hoofdstuk handelt over de CT kenmerken van de normale schildklier bij de hond. De gemiddelde pre- en post-contrast attenuatie waarden waren zeer hoog voor weke delen. Na injectie van intraveneus contrast nam het schildklier volume toe. Alle schildklierlobben zagen er homogeen uit op zowel pre- als post-contrastbeelden. De ligging, de grootte en de vorm van de schildklierlobben werden beschreven. Bijschildklieren werden niet gezien en een isthmus werd slechts bij 1 op de 25 honden aangetroffen. Gezien de uitstekende zichtbaarheid en kenmerkende eigenschappen van de normale schildklier bij de hond besloten we dat het gebruik van CT voordelig zou kunnen zijn om het onderscheid te maken tussen nekmassa’s afkomstig van schildklierweefsel en nekmassa’s van andere oorsprong. CT heeft eveneens een potentiële rol bij het stageren van schildkliertumoren. Tot slot beschreven we de MRI kenmerken van de normale schildklier. De kenmerkende vorm, ligging en intensiteit vergeleken met de omliggende structuren maakten de schildklier duidelijk herkenbaar bij alle honden. Een isthmus werd slechts bij 1 op de 44 honden aangetroffen en bijschildklieren werden niet gezien. Gezien de uitstekende zichtbaarheid en kenmerkende eigenschappen van de schildklier op MRI werd er besloten dat MRI kan bijdragen tot de diagnose van diffuse schildklieraandoeningen, bij het onderscheiden van nekmassa’s van schildklieroorsprong en andere oorsprong, en bij de stagering en operatieplanning van schildkliertumoren.
Seven dogs with thyroid gland carcinoma were treated with 131I and hormone suppressive therapy either alone (3 dogs) or in combination with surgery (3 dogs) or 137Cs teletherapy and chemotherapy (1 dog). Empirically chosen doses of 75 to 137 mCi of 131I were given orally (2 dogs) and intravenously (5 dogs). Adverse effects were limited to acute, transient bone marrow hypoplasia and pancytopenia. Nominal objective reduction in tumor volume or size and number of pulmonary metastases was observed in 4 dogs treated with 131I and thyroxine. Of these 4 dogs, 2 had stable disease for periods of 4 and 12 months while a third dog had stable disease for 27 months following two 131I treatments at 3 month intervals. The fourth dog had progressive disease. Two dogs with mediastinal metastases showed reduction in localization of 99mTc pertechnetate and radioiodine following 2 and 3 treatments using 131I. It appears that relatively high doses of 131I can be used safely for the treatment of canine thyroid tumors and that further investigation can be justified to define its efficacy.
This review describes the advantages and disadvantages of radiography, ultrasonography, and nuclear medicine in the 2 most frequent thyroid pathologies of the dog: acquired primary hypothyroidism and thyroid neoplasia. Ultrasonography and scintigraphy remain the 2 most indicated imaging modalities for these thyroid abnormalities. However, as in human medicine, computed tomography and magnetic resonance imaging also have potential indications. This is especially the case in the evaluation of the extent, local invasiveness, and local or distant metastases of thyroid neoplasia. Based on experience with different imaging modalities in people, we suggest future directions in the imaging of the canine thyroid gland.
Congenital hypothyroidism was diagnosed in five Boxer dogs presented to the Veterinary Hospital of the University of Pennsylvania between 1978 and 1979. The dogs ranged in age from 5–19 months, and were from two unrelated litters. Congenital hypothyroidism was confirmed by serum T3 and T4 radioimmunoassay and TSH stimulation test. Serial radiographs made before and after L-thyroxine oral supplementation were studied retrospectively to evaluate the resolution of skeletal abnormalities and to compare skeletal with chronological age. On initial presentation, all five dogs had the following skeletal manifestations of congenital hypothyroidism: short broad skulls, shortened vertebral bodies, and epiphyseal dysgenesis and delayed maturation. Epiphyseal dysgenesis was most common in the humeral (n = 3) and femoral condyles (n = 4), and proximal tibia (n = 4). Accelerated epiphyseal ossification occurred during thyroid hormone supplementation. Three dogs developed osteochondrosistype lesions. Bowing of the radius and disproportionate radius and ulna length resulted in humeroradial joint widening (n = 4) and humeroulnar joint subluxation (n = 1). Degenerative joint changes in the elbows (n = 4), stifles (n = 1), and shoulder (n = 1) were more common in the older dogs.
To assess the value of thyroid scintigraphy to determine thyroid status in dogs with hypothyroidism and various non-thyroidal illnesses.
Thyroid hormone concentrations were measured and quantitative thyroid scintigraphy performed in 21 dogs with clinical and/or clinicopathological features consistent with hypothyroidism.
In 14 dogs with technetium thyroidal uptake values consistent with euthyroidism, further investigations supported non-thyroidal illness. In five dogs with technetium thyroidal uptake values within the hypothyroid range, primary hypothyroidism was confirmed as the only disease in four. The remaining dog had pituitary-dependent hyperadrenocorticism. Two dogs had technetium thyroidal uptake values in the non-diagnostic range. One dog had iodothyronine concentrations indicative of euthyroidism. In the other, a dog receiving glucocorticoid therapy, all iodothyronine concentrations were decreased. Markedly asymmetric technetium thyroidal uptake was present in two dogs. All iodothyronine concentrations were within reference interval but canine thyroid stimulating hormone concentration was elevated in one. Non-thyroidal illness was identified in both cases.
In dogs, technetium thyroidal uptake is a useful test to determine thyroid function. However, values may be non-diagnostic, asymmetric uptake can occur and excess glucocorticoids may variably suppress technetium thyroidal uptake and/or thyroid hormone concentrations. Further studies are necessary to evaluate quantitative thyroid scintigraphy as a gold standard method for determining canine thyroid function.
In the dog and cat the thyroid glands are separate lobes lying beside the trachea from about the third to the eigthth tracheal ring. They are covered ventrally by the sternohyoid and sternothyroid muscles. Normal thyroid glands are not palpable.
In six normal dogs the adrenals could be visualized as separate areas of radioactivity at 7–10 days after injection of 20–40 μCi 131I-iodocholesterol per kg of body weight. Image analysis revealed uptake values of 0.15–0.3% of the injected dose. In five dogs with pituitary-dependent hyperadrenocorticism the adrenals became visible at 3–5 days after injection of the radiopharmaceutical, with uptake values of 0.38–2.2%.
In six dogs with hyperadrenocorticism due to adrenocortical tumor the scintigraphy contributed to the diagnosis and the presurgical localization. The uptake values were within the normal range; the tumor could be observed at 3–10 days after injection.
Additional findings on adrenal asymmetry and a case of fluctuating pituitary-dependent hyperadrenocorticism are discussed.
Circulating thyroglobulin was measured in 20 dogs with thyroid cancer, using a homologous polyclonal radioimmunoassay. Plasma Tg levels exceeded the normal range in 14 (70%) dogs, and ranged from 6 to 2902 micrograms/l (median 608). Plasma Tg levels tended to decrease from follicular carcinomas to solid-follicular carcinomas, to solid carcinomas (p less than 0.05). Plasma Tg levels were also higher in scintigraphically hot tumours than in cold ones. Other relationships between circulating Tg and clinical, pathological, and functional parameters were not found, except a poor (R = 0.49) but significant (p = 0.04) correlation between Tg and T4 levels. Plasma Tg was measured before surgery and at least once during follow-up, in 9 dogs. After hemithyroidectomy, a decrease was observed in 8 dogs. In 7 of these 8 dogs, plasma Tg levels declined within the reference range at the first postoperative sample. In the ninth dog, where metastases were detected 14 months after surgical treatment, plasma Tg slightly increased, yet within normal range. It is concluded that measurement of plasma Tg levels might be useful for monitoring the postoperative course of the disease in individual dogs with thyroid cancer.
Congenital hypothyroid dwarfism was diagnosed in a family of Giant Schnauzers. Three female and two male puppies from different litters were evaluated for dwarfism, lethargy, somnolence, gait abnormalities, and constipation. On physical examination, disproportionate dwarfism (n = 5), macroglossia (n = 3), hypothermia (n = 3), delayed dental eruption (n = 3), ataxia (n = 2), and abdominal distension (n = 1) were identified. Results of initial laboratory tests showed anemia (n = 4), hypercholesterolemia (n = 4), hypercalcemia (n = 2), and transudative abdominal effusion (n = 1). Radiographic skeletal surveys disclosed epiphyseal dysgenesis and delayed skeletal maturation (n = 5). A diagnosis of hypothyroidism was established on the basis of low basal serum thyroxine concentrations that failed to increase following the administration of TSH (n = 5) and markedly reduced to absent thyroid image when evaluated with gamma camera imaging of the thyroid gland (n = 4). In the two dogs that were most thoroughly evaluated, the results of thyroid histology, prolonged TSH testing, and repeat thyroid imaging, after three daily injections of TSH, were all consistent with secondary or tertiary, rather than primary, hypothyroidism. When TSH was administered over a period of 3 consecutive days (5 IU/day, subcutaneously), serum thyroid hormone response became normal and resulted in a normal thyroid image in the two dogs re-evaluated with gamma camera imaging. Daily treatment with oral levothyroxine (20 micrograms/kg) resulted in complete remission in puppies (n = 4) treated prior to 4 months of age. The other puppy failed to attain normal breed standards for height.(ABSTRACT TRUNCATED AT 250 WORDS)
Radioactive iodine (131I) was used in the treatment of a 12-year-old female dog with hyperthyroidism resulting from a large, unresectable (and metastatic) thyroid carcinoma associated with signs of severe inspiratory stridor and dyspnea. Hyperthyroidism was diagnosed on the basis of clinical signs (polyuria, polydipsia, polyphagia, weight loss, nervousness) and high basal serum thyroxine (T4) concentrations, as well as thyroid radioiodine kinetic studies that showed a high radioiodine uptake into the thyroid (% thyroid uptake) and markedly increased serum concentrations of protein-bound iodine-131 (PB131I) after 131I tracer injection. Thyroid imaging revealed diffuse radionuclide accumulation by the tumor, which involved both thyroid lobes. The dog was treated with three large doses of radioiodine (131I), ranging from 60 to 75 mCi, given at intervals of 5 to 7 months. The dog became euthyroid, and the size of the tumor decreased by approximately 25% after each 131I treatment, improving the severe inspiratory stridor and dyspnea, but both the hyperthyroid state and breathing difficulty recurred within a few months of each treatment. The dog was euthanatized 5 months after the last treatment because of progressive tracheal compression and pulmonary metastasis.
In vivo measurements of 131I levels in Japanese quail were made at 1-cm intervals from head to tail 8 times during 6 days. The ovaries of 10 good layers accumulated 4–10 times the quantities of radioiodide found in the thyroids. Radiation maxima occurred over the ovary during the first 6 hr, over the shell gland at 48 hr, and in the eggs laid during day 3. The cumulative total for 131I in the 90 eggs laid during 10 days was 64.5%. Autoradiographs showed thin radioactive deposits in the yellow yolk. The yolk under the blastodisc was unlabeled.
Four clinical cases of insulinoma in the dog are described. In each, nervous signs increased in frequency and severity over a period of approximately 4 months. Diagnosis was made on clinical signs, blood glucose concentration, response to glucose therapy and, in the 2 cases in which an radioimmunoassay was performed, blood insulin levels. Differential diagnosis and management regimes for insulinomas are discussed. Neocropsy confirmed the diagnoses in 3 cases, with multiple pancreatic lesions being present in 2, and metastases in all 3.