Thyroidal handling of radioiodine in sea level residents exposed to hypobaric hypoxia

Abstract

In the present investigation thyroidal accumulation of radioiodine and its release were assessed by direct testing of thyroid function using radioactive iodine, in vivo, in sea level residents intermittently exposed to hypobaric hypoxia. Thyroidal accumulation of radioiodine and its turnover were examined daily for 14 days. Twelve healthy human male volunteers were divided into three groups, with an equal number of individuals in each group. A decompression chamber was used to expose each group of subjects to hypoxic conditions at a simulated altitude of 3810 m for 8 h/day for 14 days. An oral dose of 25 mu Ci iodine-131 was administered to each individual of the first group immediately before the initiation of intermittent hypoxia. The second group of subjects received a tracer dose at the beginning of the 4th day of the 14 days, intermittent exposure to hypoxia, while the third group received the tracer dose 1 week after the completion of the exposure. Control studies were carried out on the subjects before they were subjected to the experimental conditions. Thyroidal accumulation of 131I in experimental subjects during the hypoxic state and in the post-hypoxic state was higher than in the control studies. The pattern of accumulation during exposure to hypoxia and in the post-hypoxic state showed multiple peaks of radioactive iodine uptake (PRAIU), a unique feature. The multiple PRAIU by the thyroid in experimental subjects were sharp and of short duration, reflecting an increased rate of 13I release from the thyroid. Control subjects had a single PRAIU by the thyroid 24 h after the administration of tracer.

Relation of Different Components of Climate with Human Pituitary-Thyroid Axis and FT3/FT4 Ratio: A Study on Euthyroid and SCH Subjects in Two Different Seasons

“…So far, the data obtained from both the cold and temperate climates have not been very conclusive as most of the studies have been done at high altitudes, where along with the temperature, factors such as hypobaric condition, changes in oxygen partial pressure, and increased ultraviolet radiation might affect the secretion of hormones. A study conducted in a hypobaric chamber demonstrated that a simulated altitude of 3810 m affects the TH level [28]. The studies are also influenced by the sleep pattern, dietary changes, and plasma volume shifts [29].…”

Preliminary screening of biomarkers in HAPE based on quasi-targeted metabolomics

“…Research shows that it has excitatory effects on almost all tissues and has a certain correlation with energy metabolism (proteins, sugars, and fats), thermoregulation, tissue differentiation, and growth and development of bodies ( Maria et al, 2019 ). Hypoxia at high altitudes leads to changes in thyroid function and structure ( Naeije, 2010 ); however, the results of previous studies on the changes in TH caused by hypoxia are inconsistent ( Rawal et al, 1993 ; Savourey et al, 2004 ; Barnholt et al, 2006 ). Thyroid function has been shown to be enhanced, weakened, or even unchanged, which is related to many factors such as the exposure mode of hypoxia, altitude, duration, and availability of altitude adaptive training.…”

Endocrine Function

“…An increase in protein-bound iodine, fi rst reported in 1966 [ 47 ], has been confi rmed by observations of increased uptake and release of iodine from the thyroid gland [ 48 ]. Most authors agree that high altitude induces an elevation in plasma concentration of both free and total T4 fractions of thyroxin [ 30 , 47 , 49 -57 ].…”