Abstract

A 30-year-old intact female Bornean orangutan (Pongo pygmaeus pygmaeus) was presented as a non-reproductive animal with a sparse haircoat, obesity (104 kg), lethargy, and consistent migration towards warmth. Previous history had included superovulatory drug stimulation without reproductive success. Dietary management did not alter its clinical signs.

Initial evaluation of its clinical status in 1993 revealed normal reproductive tract anatomy (via ultrasound, hormonal values, and vaginal cytology) but low values for 3, 5, 3’, 5’-tetraiodothyronine (T₄=3.3 µg/dL, range=4.5–12.0 µg/dL) and free 3, 5, 3’-triiodothyronine (T₃=139 ng/dL, range=230–420 ng/dL) when compared with human normal reference values.^1,2 Values for thyroid stimulating hormone (TSH) were considered normal (3.28 ng/mL, range=0.35–5.50 ng/mL), as were values for serum cortisol (2.5 µg/dL, range=1.0–4.0 µg/dL) when compared to human reference normals.^1,2 The complete blood count and serum chemistry profile demonstrated a fasting hypercholesterolemia (347 mg/dL, range=100–200 mg/dL) which was also compatible with a clinical diagnosis of hypothyroidism.¹ The rest of the complete blood count and serum chemistries were unremarkable, as were several urinalyses.

The orangutan was placed on synthetic levothyroxine sodium (Synthyroid, Knoll Pharmaceutical Company, Mount Olive, NJ, USA) according to a therapeutic protocol developed for elderly humans (K.A. Alm, personal communication). Basically, a morning synthroid tablet of 0.05 mg for 2 weeks, followed by 0.10 mg for 2 weeks, then 0.15 mg for 2 weeks, and finally its current dose of 0.20 mg is administered PO every 24 hours. Side effects noted were an increase in activity levels and mentation.

To monitor thyroid levels, the orangutan care staff has trained the orangutans to utilize a “blood sleeve” whereby the animal sits still for blood sampling from the antebrachium or the back of the hand. In this manner, T₃, T₄, and TSH values are routinely monitored. Blood samples are taken 6–8 hours and 24 hours after administration of levothyroxine.¹ In addition, complete blood counts and serum chemistries are monitored without immobilization.

The orangutan has lost 60 kg during the 4 years it has been supplemented with levothyroxine, and reevaluation of T₃, T₄, and TSH values are within normal limits (T₃=274 ng/dL; T₄=10.76 µg/dL). In addition, its mental status, hair coat and activity level have improved greatly. The cholesterol levels have decreased from a high of 347 mg/dL to current levels of 190 mg/dL. Unfortunately, correction of this underlying problem has not resulted in conception. Further investigation into its reproductive soundness is continuing. In addition, further testing of thyroid function is continuing in two orangutans that are clinically normal.

This case represents a true team effort in addressing this orangutan’s problem, and monitoring its progress. Without the access to routine collection blood, it is unlikely that it would be immobilized to monitor thyroid levels. This orangutan continues to do well 4 years after the initiation of thyroid supplementation.

Acknowledgments

The author would like to thank the orangutan care staff for their intense efforts in training this animal to allow routine blood sampling.

Literature Cited

1.  Chastain CB, Ganjam VK. Clinical Endocrinology of Companion Animals. Philadelphia, PA: Lea & Febiger; 1986:135–155.

2.  Roche Biomedical Laboratories, Burlington, North Carolina.