Fluctuations in thyroid function, under normal and pathological conditions, in relation to the circadian rhythm
Title:
Fluctuations in thyroid function, under normal and pathological conditions, in relation to the circadian rhythm
Author:
Balogh, L.
Appeared in:
Biological rhythm research
Paging:
Volume 3 (1972) nr. 2 pages 206
Year:
1972-08
Contents:
The somewhat modified method of West et al. was used to determine the thyroxine content of the blood. Another sample extracted for thyroxine in,the same way was submitted to alkaline ashing before the ceri-catalytic iodine determination. In venous blood taken simultaneously from patients with evidently different functional state of the gland, i.e. from cases with florid hyperthyroidism, one month after subtotal thyroidectomy and from healthy persons, the difference between the two methods did not exceed 10%, whereas absolute figures obtained without ashing were 7.2, 1.4, and 2.7 μg/100 ml plasma, respectively, indicating that results obtained by this method represent iodothyroxines of thyroidal origin. Therefore, they were called in a preliminary way ThGland. On the other hand, taking the blood from the pulmonal and femoral arteries at the same time, no difference could be found in plasma ThG whereas in the blood taken from the femoral artery the difference between the two methods was 50% above that in blood taken from the pulmonal artery. The difference between the two methods (ThTotal-ThGland) was called for the sake of convenience ThLung to imply that this fraction probably originated in the lungs. Readings for the BMR and for the three kinds of Th data were taken at 6.00, 8.00, 10.00 and 12.00 hr from clinically healthy persons. The weighted means of the individual regression coefficients on time proved to be positive for BMR, ThT and ThL and negative for ThG. BMR and Th values in patients suffering from diffuse toxic, goiter showed the same patterns of response as did healthy persons in the course of the diurnal variation though absolute figures for BMR, Thy and ThG are markedly elevated. On the other hand, in cases of another type of hyperthyroidism (multinodular toxic goiter) all parameters observed showed inverse changes in the course of the circadian rhythm, i.e. negative regression coefficients on time for BMR, ThT, ThL and a positive one for ThG. Subtotal thyroidectomy for multinodular toxic goiter restores the normal response in the course of the diurnal variation. It is postulated that iodo-thyroxines of unknown origin are being formed in the lungs and their concentration is increasing in the forenoon course of the circadian rhythm associated with an increasing BMR. The presence of a feed back mechanism on the thyroid is discussed.
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