Serum Thyroid Hormone Values for African Spurred Tortoises (Centrochelys [Formerly Geochelone] sulcata)

ABSTRACT Hypothyroidism has been reported in Galapagos (Geochelone nigra [formerly G. elephantopus]) and Aldabra (G. gigantea) tortoises, and reference values for thyroxine (T4) are available for these two species. Hypothyroidism also has been presumptively diagnosed in an African spurred tortoise (Centrochelys [formerly G.] sulcata) based on clinical disease and response to therapy, but no reference values were available to confirm the disease. Twelve clinically normal African spurred tortoises from a private collection were used to obtain blood for serum thyroid hormone analysis. The median values for the different thyroid hormones were as follows: T4, 4.0 nmol/L (0.31 mcg/dl); free thyroxine (fT4), 4.0 pmol/L (0.31 ng/dl); triiodothyronine (T3), 0.15 nmol/L (0.01 mcg/dl); and free triiodothyronine (fT3), 2.9 pmol/L (0.189 ng/dl). The descriptive measures for T4, fT4, T3, and fT3 from this study are proposed by us as initial thyroid hormone reference values for the African spurred tortoise. The serum T4...