This study certainly seems to throw up a number of questions - but few or no answers. Fascinating and I sincerely hope that the full paper eventually becomes accessible on-line.
Endocrinology. 2013 Oct 3. [Epub ahead of print]
Thyroid autoantibodies are rare in non-human great apes and hypothyroidism cannot be attributed to thyroid autoimmunity.
Aliesky H, Courtney CL, Rapoport B, McLachlan SM.
Thyroid Autoimmune Disease Unit, Cedars-Sinai Research Institute and UCLA School of Medicine, Los Angeles, CA.
The great apes include, in addition to Homo, the genera Pongo (orangutans), Gorilla (gorillas), and Pan, the latter comprising two species, P.troglodytes (chimpanzees) and P.paniscus (bonobos). Adult-onset hypothyroidism was previously reported in four individual non-human great apes. However, there is scarce information on normal serum thyroid hormone levels and virtually no data for thyroid autoantibodies in these animals. Therefore, we examined thyroid hormone levels and TSH in all non-human great ape genera including adults, adolescents and infants. Because hypothyroidism in humans is commonly the end-result of thyroid autoimmunity, we also tested healthy and hypothyroid non-human great apes for antibodies to thyroglobulin (Tg), thyroid peroxidase (TPO) and the thyrotropin-receptor (TSHR). We established a thyroid hormone and TSH database in orangutans, gorillas, chimpanzees and bonobos (447 individuals). The most striking differences are the greatly reduced free-T4 and free-T3 levels in orangutans and gorillas versus chimpanzees and bonobos, and conversely, elevated TSH levels in gorillas versus Pan species. Antibodies to Tg and TPO were only detected in 2.6% of adult animals versus ∼10% in humans. No animals with Tg, TPO or TSHR antibodies exhibited thyroid dysfunction. Conversely, hypothyroid non-human great apes lacked thyroid autoantibodies. Moreover, thyroid histology in necropsy tissues was similar in euthyroid and hypothyroid individuals and lymphocytic infiltration was absent in two hypothyroid animals. In conclusion, free-T4 and free T3 are lower in orangutans and gorillas versus chimpanzees and bonobos, the closest living human relatives. Moreover, thyroid autoantibodies are rare and hypothyroidism is unrelated to thyroid autoimmunity in non-human great apes.
[PubMed - as supplied by publisher]
Picture: Orangutan (Pongo pygmaeus) feeding in Sepilok rehabilitation center, Borneo, Malaysia: Author =Nino Verde