Validation of Immunoassays for Total Thyroxine and Free Thyroxine and Age and Sex‐Related Variation in Thyroid Hormone Serum Concentrations in Orangutans ( <i>Pongo</i> sp.)

BACKGROUND: Thyroid disease is reported in orangutans, but to properly diagnose and manage these disorders, reference intervals for circulating thyroid hormones are needed. METHODS: ), and thyroid-stimulating hormone (TSH). RESULTS: . CONCLUSIONS: Age and sex-related variation in circulating thyroid hormone concentrations in orangutans is described. Elevated TSH levels are the most consistent finding in orangutans with clinical signs of hypothyroidism.