[Functional activity of the pituitary-thyroid gland system during 370-day anti-orthostatic hypokinesia].

The concentrations of the thyrotrophic hormone (TTH). bound thyroxine (T4), free thyroxine (FT4), and triiodothyronine (T3) were measured by RIA in the blood of 10 test subjects during a 370-day head-down tilt study and a 250-day recovery period after it. The concentrations of TTH, FT4, and T3 decreased during bed rest and did not return to norm during recovery.

[Studies of the morphology of the thyroid gland and thyroid hormone levels in the blood of rats in experiments on "Kosmos-1667" and "Kosmos-1887"].

Using histological, electron microscopic, and biochemical (measurement of total thyroxine, free thyroxine and triiodothyronine in plasma) method, thyroid glands of 17 male rats of the Wistar SPF strain flown for 7 days on Cosmos-1667 and for 13 days on Cosmos-1887 were investigated. It was found that a longer exposure to space flight effects (for 13 days) led to a thyroid activity decline (significant reduction of thyrocyte size and nuclear area, accumulation of colloid drops in the cytoplasm, decrease of iodinated thyroglobulins in the colloid, etc.) together with a substantial decrease of T4 and T3 in plasma.