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Keywords:

  • Melanin;
  • Phenylalanine;
  • Thyroxine;
  • Tyrosine

Background

Hyperthyroidism is common among older cats, but its pathogenesis remains poorly understood. Siamese and Himalayan cats have a reduced risk of hyperthyroidism compared with domestic short-hair cat breeds. A mechanism of risk reduction in pointed-coat breeds is unknown.

Objectives

To determine if tyrosine, phenylalanine, iodine, or selenium blood concentrations are altered in hyperthyroid cats and to describe the plasma amino acid profiles of client-owned cats with naturally occurring hyperthyroidism.

Animals

Twenty-seven client-owned cats with (n = 12) and without (n = 15) hyperthyroidism were studied.

Methods

Cross-sectional study. Hyperthyroid cats were prospectively recruited among cats presenting for radioiodine therapy. Control cats were recruited among pets of hospital personnel. Blood was collected for total thyroxine, plasma amino acid, selenium, and iodine determination. Coat color (8 white or pointed; 19 dark), breed, and diet history were recorded.

Results

Tyrosine, phenylalanine, iodine, and selenium levels were not significantly different among light or dark cats or cats with or without hyperthyroidism (P > .05). Plasma amino acid profiles of hyperthyroid cats and control cats were similar, and neither group was deficient in any of the amino acids. l-glutamine was significantly lower in cats with hyperthyroidism (mean ± SD: 648 ± 193) compared with control cats (816 ± 134; P < .05).

Conclusions and Clinical Importance

Altered tyrosine, iodine, and selenium metabolism were not associated with coat color or hyperthyroidism in pointed or light coat–colored cats.