Master of Science / Department of Clinical Sciences / Gregory F. Grauer / Hyperthyroidism is the most common endocrinopathy of geriatric cats and has physiologic effects on almost every organ in the body. It specifically affects the kidneys by increasing renal blood flow and glomerular filtration rate. In addition, activation of the renin angiotensin aldosterone system (RAAS) is increased and ultimately leads to efferent glomerular arteriole constriction and potentially glomerular hypertension. The classic treatment modalities for feline hyperthyroidism (anti-thyroid medication, radioiodine or surgery) have been evaluated for their overall effects on renal function. Studies have demonstrated that glomerular filtration rate (GFR) declines and serum creatinine increases with hyperthyroid treatment independent of the treatment modality. Hill’s® Prescription Diet® y/d® Feline, a relatively new dietary treatment modality for feline hyperthyroidism with controlled iodine concentrations, reduced phosphorus and protein, and increased omega-3 fatty acids, has been shown to significantly decrease thyroid hormone levels. The research provided in this report is the first evaluating the posttreatment effects of y/d® Feline on renal function. In agreement with previous studies, our research found that y/d® Feline resulted in a significant decrease in thyroid hormone levels. However, in contrast to other treatment modalities, y/d® Feline did not result in a significant decline in GFR, and it did result in a significant decline in mean serum creatinine concentration. These data indicate that y/d® Feline, as a treatment for feline hyperthyroidism, does not have a negative effect on renal function.

Thesis (doctoral)--Rijksuniversiteit te Groningen.

About 10% of hyperthyroid cats have a normal total T4 (TT4), requiring further testing to make the diagnosis. Thyroid stimulating hormone (TSH) is measured using the "canine" assay (TSH-CLIA, Immulite 2000 by Siemens) as the only assay currently available. However, this assay cannot differentiate between subnormal and low-normal TSH concentrations in cats due to poor specificity (70-85%). A novel feline-optimized TSH assay (TSH-BAW, Truforma by Zomedica) was recently developed. It allows differentiation between euthyroid and hyperthyroid cats. However, the effect of non-thyroidal illness (NTI) on TSH-BAW has not been evaluated. Our objectives included the comparison of serum TSH concentration using both the TSH-CLIA and TSH-BAW assays among hyperthyroid cats, cats with NTI, and healthy cats, and the evaluation of the sensitivity and specificity of the TSH-BAW for diagnosis of FHT. This prospective cross-sectional study was performed on 102 client-owned cats, including 37 hyperthyroid, 33 healthy, and 32 NTI cats. The following thyroid hormones were measured in all cats: TT4, TSH with both assays (Immulite 2000 and Truforma). Hyperthyroidism was confirmed by thyroid scintigraphy. Euthyroidism was confirmed by repeating TT4 measurement at least three months after enrollment (if available) to rule out subclinical hyperthyroidism. Cats with NTI were further divided based on the severity of their illness. Serum TSH was compared among groups using Kruskal-Wallis followed by Dunn's procedure, and compared among NTI severity scores using the Fisher's Exact test. Significance was set at P <0.05. The sensitivity and specificity of TSH-BAW for detecting hyperthyroidism are 78% (62-90%) and 97% (84-100%), respectively. The median TSH is significantly different between hyperthyroid cats and healthy and NTI cats with both assays (P<0.01). The TSH was not different between the latter euthyroid groups (P=0.87 and P=0.29). Eight (21.6%) hyperthyroid cats have a normal TSH-BAW but undetectable TSH-CLIA. Twelve (4 healthy, 8 NTI) euthyroid cats (18.5%) have an undetectable TSH-CLIA with only two (1 healthy, 1 NTI) (3%) having an undetectable TSH-BAW. The proportion of cats with a suppressed TSH is higher with severe illnesses with the TSH-CLIA only. In conclusion, the TSH-BAW has a high specificity, identifies normal TSH in healthy cats more often, and appears to not be affected by NTI. It can be a useful tool for the diagnosis of feline hyperthyroidism. However, a low-normal TSH cannot be used to rule out hyperthyroidism. / Master of Science / Hyperthyroidism leads to elevation of the thyroid hormone total T4 (TT4). About 10% of hyperthyroid cats have a normal TT4, requiring further testing to make the diagnosis. Another thyroid hormone, thyroid stimulating hormone (TSH), could be used like it is with people. In feline medicine, it is measured using the "canine" assay (TSH-CLIA, Immulite 2000 by Siemens) as the only assay currently available. However, this assay cannot differentiate between subnormal and low-normal TSH concentrations in cats due to poor specificity (70-85%). A novel feline-optimized TSH assay (TSH-BAW, Truforma by Zomedica) was recently developed. It allows differentiation between euthyroid and hyperthyroid cats. However, the effect of non-thyroidal illness (NTI) on TSH-BAW has not been evaluated. Our objectives included the comparison of serum TSH concentration using both the TSH-CLIA and TSH-BAW assays among hyperthyroid cats, cats with NTI, and healthy cats, and the evaluation of the sensitivity and specificity of the TSH-BAW for diagnosis of FHT. The study was performed on 102 client-owned cats, including 37 hyperthyroid, 33 healthy, and 32 NTI cats. The following thyroid hormones were measured in all cats: TT4, TSH with both assays (Immulite 2000 and Truforma). Cats with NTI were further divided based on the severity of their illness. Serum TSH was compared among groups using Kruskal-Wallis followed by Dunn's procedure, and compared among NTI severity scores using the Fisher's Exact test. Significance was set at P <0.05. The sensitivity and specificity of TSH-BAW are 78% and 97%, respectively. The median TSH is significantly different between hyperthyroid cats and healthy and NTI cats with both assays. The euthyroid cats (healthy and NTI cats) were not different. Eight (21.6%) hyperthyroid cats have a normal TSH-BAW (not normal in the face of hyperthyroidism) but undetectable TSH-CLIA. The proportion of euthyroid cats with a suppressed TSH (not normal in the face of euthyroidism) is higher with the TSH-CLIA compared to the TSH-BAW. Only with the TSH-CLIA, the proportion of NTI cats with a suppressed TSH is higher than healthy cats, and is higher with severe illnesses. In conclusion, the TSH-BAW has a high specificity, identifies normal TSH in healthy cats more often, and appears to not be affected by NTI. It can be a useful tool for the diagnosis of feline hyperthyroidism. However, a low-normal TSH cannot be used to rule out hyperthyroidism.

Thesis--M.D., University of Hong Kong, 1982.

Objective : An audit of the use and outcomes of Radioactive Iodine (RAI) therapy in the definitive management of thyrotoxicosis at Inkosi Albert Luthuli Central Hospital (IALCH), KwaZulu-Natal, South Africa. Methods : The clinical records of all new patients with thyrotoxicosis, referred in a 4 year period between 01/01/2003 and 31/12/2006, were analysed. Response to RAI was monitored using biochemical parameters (namely, Thyroid Stimulating Hormone and Free T4 levels). Rates of euthyroidism (cure), hypothyroidism and hyperthyroidism (treatment failure) were correlated to dose of RAI. Patients were followed-up for at least 2 years or until the onset of hypothyroidism. The follow-up period was until 31/12/2007. Results : One hundred and fourteen patients (37.7%), of a cohort of 302 new thyrotoxic patients treated with RAI, met the inclusion criteria. Ninety-six patients (84.2%) had Graves Disease (GD) whilst 18 had Toxic Nodular Disease (TND). At 2 year follow-up, 91 patients (79.8%) were hypothyroid, 10 (8.8%) were euthyroid and 13 (11.4%) were hyperthyroid. The average dose of RAI to achieve euthyroidism was 10mCi and hypothyroidism, 9.7mCi. The average time to achieve euthyroidism was 5.9 months and 10.1 months to become hypothyroid. Thirty-one patients (27.2%) remained persistently hyperthyroid after one dose of RAI. Patients with GD (88.5%) were more likely to become hypothyroid (p < 0.001) whilst 38.9% of TND patients remained hyperthyroid (p = .001). Baseline TFT values were significant in terms of outcomes correlated with the prescribed RAI dose i.e Low Dose (<8mCi) vs. Intermediate Dose (8-9mCi) vs. High Dose (>9mCi)(TSH p = 0.05; FT4 p = 0.003; FT3 p = 0.001). Conclusion : The majority of patients became hypothyroid over time, in keeping with reported data. In the public health sector, where early access to RAI (in terms of waiting times for appointments for RAI) and follow-up are major problems, early cure is essential to minimize the morbidity of thyrotoxicosis and this may be achieved with an initial high dose of RAI. / Thesis (M.Med.)-University of KwaZulu-Natal, Durban, 2011.

"Publication authorized September 2, 1943." / Includes bibliographical references (p. 69-75).

Thesis (M.S.M.E.)--University of Massachusetts Amherst, 2009. / Open access. "This protocol is the basis of an ongoing pilot study in conjunction with Cooley Dickinson Hospital, Northampton, MA."--P. vii. Includes bibliographical references (p. 118-121).

Thesis (doctoral)--Katholieke Universiteit te Nijmegen.

Thesis (M.D.)--University of Hong Kong, 1982. / Also available in print.

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