Quantitative thyroid scintigraphy in greyhounds suspected of primary hypothyroidism

Effect of recombinant human thyrotropin on the uptake of radioactive iodine (¹²³I) in dogs with thyroid tumors

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.

Clinical pathology of Greyhounds and other sighthounds

Owing to the development of Greyhounds as racing sighthounds, these dogs have acquired unique physiologic adaptations that distinguish them from other breeds. Reference intervals for many analytes in retired racing Greyhounds (RRGs) differ from those of other breeds; most of the hematologic differences have also been described in other sighthounds. In this review, we provide a survey of the literature on clinical pathology of Greyhounds and other sighthounds and results of laboratory testing, including analysis of CBCs, biochemical profiles, coagulation tests, and blood gases, in RRGs at The Ohio State University. Major clinicopathologic differences in this breed include higher RBC mass, creatinine concentration, glomerular filtration rate, activities of hepatic enzymes, and concentration of cardiac troponin, as well as lower WBC, neutrophil, and platelet counts, thromboelastographic values, and concentrations of serum haptoglobin, total globulins, and T4.

Canine hypothyroidism: a review of aetiology and diagnosis

Hypothyroidism is recognised as an important endocrine disorder of dogs, and a frequent differential for numerous presenting complaints. Its diagnosis has never been straight forward as results suggestive of hypothyroidism can occur for a variety of reasons in dogs with normal thyroid function (euthyroid). As a consequence, the accurate investigation of hypothyroidism has been hindered by the potential inclusion of a number of cases not truly hypothyroid. In recent years, the development of newer diagnostic tests, e.g. free thyroxine, canine thyroid stimulating hormone, thyroglobulin autoantibodies, has significantly improved our ability to reliably differentiate hypothyroidism from other clinically similar disorders. This has led to a marked increase in our knowledge of the phenotypic, genotypic and aetiological aspects of this disorder in dogs.

Effect of recombinant human TSH on the uptake of radioactive iodine ((123)I) by the thyroid gland in healthy beagles

In human medicine, recombinant human thyroid-stimulating hormone (rhTSH) increases thyroid radioactive iodine uptake (RAIU), allowing radioiodine-131 ((131)I) dose reduction and greater efficacy in the treatment of differentiated thyroid cancer and multinodular goiter. The goal of this study was to evaluate the effect of rhTSH, administered 24 h and 48 h before radioiodine-123 ((123)I), on the thyroid RAIU in healthy dogs. Seven healthy euthyroid beagles were randomly allocated to 3 groups (2 groups of 2 dogs and 1 group of 3 dogs) in a prospective, blinded, crossover study. At Week 1, 1 group received (123)I for a baseline RAIU; 1 group received 100 μg of rhTSH IV 24 h before (123)I, and 1 group received 100 μg of rhTSH IV 48 h before (123)I. All dogs received 37 MBq of radioactive (123)I IV, and thyroid RAIU was determined 8 h, 24 h, and 48 h thereafter. The study was designed in such a manner that each dog received the 3 treatments and a wash-out period of 3 wk was respected in between. Blood samples were taken for measurement of serum total thyroxine (TT4) and thyrotropin (TSH) concentrations at baseline and 6 h, 12 h, 24 h, and 48 h after rhTSH administration. Recombinant human TSH caused no significant change on thyroid RAIU. The overall mean thyroid RAIU significantly decreased during the study independent of the treatment. Recombinant human TSH significantly increased serum TT4 concentration, which peaked 6 h after rhTSH administration. Compared to baseline, serum TSH concentration remained higher at 6 h, 12 h, 24 h, and 48 h. However, a statistically significant difference was reached only at 6 h and 12 h after rhTSH administration. No adverse effects of rhTSH were observed during the study. Further studies are needed to determine the best timing and dosage of administration of rhTSH in healthy and thyroid carcinoma dogs.