THYROID STATUS OF DOGS CONTINUOUSLY EXPOSED TO ONE-HALF ATMOSPHERE

Six male beagle dogs were maintained on ambient air at one-half atmosphere for 33 days and were monitored for protein-bound iodine PBI, thyroid I 131 avidity, plasma triiodothyronine uptake, and plasma 17-hydroxycorticosteroids. Data were compared with those from littermate controls held at ground level. Increased I 131 uptake and reduced triiodothyronine uptake were observed in the altitude-exposed dogs, while no change in the peripheral blood hydrocortisone level was seen. No difference in the gross, microscopic, or ultrastructural anatomy of the thyroid glands of groups was noted.