Thyroid Testing in Cats

van Hoek IM, Vandermeulen E, Peremans K et al: Thyroid stimulation with recombinant human thyrotropin in healthy cats, cats with non-thyroidal illness and in cats with low serum thyroxin and azotaemia after treatment of hyperthyroidism, J Feline Med Surg 12:117, 2010.

Investigators studied the recombinant human thyrotropin (rhTSH) stimulation test in healthy cats (Group 1), cats with non-thyroidal illness (Group 2) and cats with low serum total T4 (TT4) and azotemia after I-131 treatment (Group 3). Radioiodine (131)is the treatment of choice for hyperthyroidism, yet iatrogenic hypothyroidism can occur in 6-30% of cases post-treatment. Complicating this, up to 39% of treated cats have chronic kidney disease (CKD). When a low circulating serum TT4 concentration is found in cats treated with I-131, non-thyroidal illness (NTI) has to be considered, especially CKD, before a diagnosis of iatrogenic hypothyroidism can be confirmed. With the consideration that hypothyroidism can decrease renal function, a diagnosis of hypothyroidism or NTI is necessary. Serum TT4 increased significantly in groups 1 and 2, but not in group 3 after rhTSH administration. Post-rhTSH serum TT4 concentrations differed significantly between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. Based on the marginal increase in serum TT4 concentration, compared to the healthy cats and cats with NTI, the conclusion was that all four cats from Group 3 had iatrogenic hypothyroidism. The study results suggest a TT4 measurement before and after rhTSH is a clinically useful test and can reliably evaluate thyroid function and differentiate euthyroidism from iatrogenic hypothyroidism in cats. [VT]

Related articles:
van Hoek IM, Peremans K, Vandermeulen E et al: Effect of recombinant human thyroid stimulating hormone on serum thyroxin and thyroid scintigraphy in euthyroid cats, Journal of Feline Medicine & Surgery 11:309, 2009.

More on cat health: Winn Feline Foundation Library
Join us on Facebook
Follow us on Twitter
Subscribe to our e-newsletter

van Hoek IM, Vandermeulen E, Peremans K et al: Thyroid stimulation with recombinant human thyrotropin in healthy cats, cats with non-thyroidal illness and in cats with low serum thyroxin and azotaemia after treatment of hyperthyroidism, J Feline Med Surg 12:117, 2010.

Investigators studied the recombinant human thyrotropin (rhTSH) stimulation test in healthy cats (Group 1), cats with non-thyroidal illness (Group 2) and cats with low serum total T4 (TT4) and azotemia after I-131 treatment (Group 3). Radioiodine (131)is the treatment of choice for hyperthyroidism, yet iatrogenic hypothyroidism can occur in 6-30% of cases post-treatment. Complicating this, up to 39% of treated cats have chronic kidney disease (CKD). When a low circulating serum TT4 concentration is found in cats treated with I-131, non-thyroidal illness (NTI) has to be considered, especially CKD, before a diagnosis of iatrogenic hypothyroidism can be confirmed. With the consideration that hypothyroidism can decrease renal function, a diagnosis of hypothyroidism or NTI is necessary. Serum TT4 increased significantly in groups 1 and 2, but not in group 3 after rhTSH administration. Post-rhTSH serum TT4 concentrations differed significantly between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. Based on the marginal increase in serum TT4 concentration, compared to the healthy cats and cats with NTI, the conclusion was that all four cats from Group 3 had iatrogenic hypothyroidism. The study results suggest a TT4 measurement before and after rhTSH is a clinically useful test and can reliably evaluate thyroid function and differentiate euthyroidism from iatrogenic hypothyroidism in cats. [VT]

Related articles:
van Hoek IM, Peremans K, Vandermeulen E et al: Effect of recombinant human thyroid stimulating hormone on serum thyroxin and thyroid scintigraphy in euthyroid cats, Journal of Feline Medicine & Surgery 11:309, 2009.

More on cat health: Winn Feline Foundation Library
Join us on Facebook
Follow us on Twitter
Subscribe to our e-newsletter

Read More

Kidney Insufficiency After Treatment for Feline Hyperthyroidism

Riensche, M. R., T. K. Graves, et al. (2008). "An investigation of predictors of renal insufficiency following treatment of hyperthyroidism in cats." J Feline Med Surg 10(2): 160-6.

Renal insufficiency is a common finding in older cats, affecting about 30% of cats over age 15. Hyperthyroidism is the most common endocrine disorder in cats, and it appears to be increasing in incidence over time. Hyperthyroidism can mask underlying renal disease by causing an increase in the glomerular filtration rate (GFR). Treatment of hyperthyroidism leads to a decrease in GFR and an increase in blood urea nitrogen (BUN). Different treatments exist for hyperthyroidism in cats, including reversible (methimazole) and irreversible (thyroidectomy, radioiodine) options. The ability to predict which cats will develop renal insufficiency after treatment for hyperthyroidism would help guide treatment decisions. The purpose of this retrospective study was to determine if routine pre-treatment clinical data can be used to predict the development of overt renal insufficiency following treatment of feline hyperthyroidism. Medical records were reviewed for 39 nonazotemic cats undergoing treatment for hyperthyroidism at the College of Veterinary Medicine, University of Illinois. The records were reviewed for for signalment, clinical signs, and serum biochemical, hematologic and urinalysis findings before and after treatment for hyperthyroidism. Cats that developed renal insufficiency within 6 months after treatment (n=20) were compared to cats that did not (n=19). No significant differences could be detected between the groups with respect to the parameters measured. The study suggests that the results of routine pre-treatment clinical data cannot be used to predict renal function after treatment for hyperthyroidism, and that a trial of methimazole therapy is indicated before choosing irreversible treatment such as radioiodine.
>> PubMed abstract

Related articles:
Boag, A. K., R. Neiger, et al. (2007). "Changes in the glomerular filtration rate of 27 cats with hyperthyroidism after treatment with radioactive iodine." Vet Rec 161(21): 711-5.
>> PubMed abstract

More on cat health: Winn Feline Foundation Library

Riensche, M. R., T. K. Graves, et al. (2008). "An investigation of predictors of renal insufficiency following treatment of hyperthyroidism in cats." J Feline Med Surg 10(2): 160-6.

Renal insufficiency is a common finding in older cats, affecting about 30% of cats over age 15. Hyperthyroidism is the most common endocrine disorder in cats, and it appears to be increasing in incidence over time. Hyperthyroidism can mask underlying renal disease by causing an increase in the glomerular filtration rate (GFR). Treatment of hyperthyroidism leads to a decrease in GFR and an increase in blood urea nitrogen (BUN). Different treatments exist for hyperthyroidism in cats, including reversible (methimazole) and irreversible (thyroidectomy, radioiodine) options. The ability to predict which cats will develop renal insufficiency after treatment for hyperthyroidism would help guide treatment decisions. The purpose of this retrospective study was to determine if routine pre-treatment clinical data can be used to predict the development of overt renal insufficiency following treatment of feline hyperthyroidism. Medical records were reviewed for 39 nonazotemic cats undergoing treatment for hyperthyroidism at the College of Veterinary Medicine, University of Illinois. The records were reviewed for for signalment, clinical signs, and serum biochemical, hematologic and urinalysis findings before and after treatment for hyperthyroidism. Cats that developed renal insufficiency within 6 months after treatment (n=20) were compared to cats that did not (n=19). No significant differences could be detected between the groups with respect to the parameters measured. The study suggests that the results of routine pre-treatment clinical data cannot be used to predict renal function after treatment for hyperthyroidism, and that a trial of methimazole therapy is indicated before choosing irreversible treatment such as radioiodine.
>> PubMed abstract

Related articles:
Boag, A. K., R. Neiger, et al. (2007). "Changes in the glomerular filtration rate of 27 cats with hyperthyroidism after treatment with radioactive iodine." Vet Rec 161(21): 711-5.
>> PubMed abstract

More on cat health: Winn Feline Foundation Library

Read More