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Thyroid hormone metabolism in thyroid disease as reflected by the ratio of serum triiodothyronine to thyroxine.
J Endocrinol Invest. 1986 Oct; 9(5):407-12.JE

Abstract

In 77 euthyroid subjects the mean ratio between serum triiodothyronine (S-T3) in nmol/l X 10(3) and serum thyroxine (S-T4) in nmol/l was 22.4 with a standard deviation of 4.3. The distribution of the ratio was close to Gaussian. It was not changed in subjects under estrogen effect. The ratio was increased in hypothyroid subjects suggesting a mechanism preserving S-T3 better than S-T4 in thyroid failure. This mechanism seemed independent of TSH as the increasing S-T3/S-T4 ratio in primary hypothyroidism was not correlated to serum TSH (S-TSH), and patients with hypothyroidism of pituitary origin, without any increase in S-TSH, had a significantly elevated S-T3/S-T4 ratio. In subjects taking thyroxine, S-T4 but not S-T3 increased with the dose of thyroxine, leading to decreasing S-T3/S-T4 ratios. This indicates a mechanism that keeps S-T3 within normal limits also when the S-T4 supply is high. This applied also to athyreotic subjects on thyroxine and to subjects on thyroxine plus carbimazole, suggesting that the mechanism is independent of thyroid tissue, uninfluenced by carbimazole, and probably operates via the peripheral metabolism of T4. Changes in the S-T3/S-T4 ratio can be achieved by several mechanisms, and the specificity of ratio changes is low. However, by investigating the ratio S-T3/S-T4 in selected clinical states we can depict the ability of the organism to protect its normal S-T3 level in situations with divergent S-T4 concentrations, even if details about the mechanisms cannot be explained.

Authors

No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

3794185

Citation

Erfurth, E M., and P Hedner. "Thyroid Hormone Metabolism in Thyroid Disease as Reflected By the Ratio of Serum Triiodothyronine to Thyroxine." Journal of Endocrinological Investigation, vol. 9, no. 5, 1986, pp. 407-12.
Erfurth EM, Hedner P. Thyroid hormone metabolism in thyroid disease as reflected by the ratio of serum triiodothyronine to thyroxine. J Endocrinol Invest. 1986;9(5):407-12.
Erfurth, E. M., & Hedner, P. (1986). Thyroid hormone metabolism in thyroid disease as reflected by the ratio of serum triiodothyronine to thyroxine. Journal of Endocrinological Investigation, 9(5), 407-12.
Erfurth EM, Hedner P. Thyroid Hormone Metabolism in Thyroid Disease as Reflected By the Ratio of Serum Triiodothyronine to Thyroxine. J Endocrinol Invest. 1986;9(5):407-12. PubMed PMID: 3794185.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Thyroid hormone metabolism in thyroid disease as reflected by the ratio of serum triiodothyronine to thyroxine. AU - Erfurth,E M, AU - Hedner,P, PY - 1986/10/1/pubmed PY - 1986/10/1/medline PY - 1986/10/1/entrez SP - 407 EP - 12 JF - Journal of endocrinological investigation JO - J. Endocrinol. Invest. VL - 9 IS - 5 N2 - In 77 euthyroid subjects the mean ratio between serum triiodothyronine (S-T3) in nmol/l X 10(3) and serum thyroxine (S-T4) in nmol/l was 22.4 with a standard deviation of 4.3. The distribution of the ratio was close to Gaussian. It was not changed in subjects under estrogen effect. The ratio was increased in hypothyroid subjects suggesting a mechanism preserving S-T3 better than S-T4 in thyroid failure. This mechanism seemed independent of TSH as the increasing S-T3/S-T4 ratio in primary hypothyroidism was not correlated to serum TSH (S-TSH), and patients with hypothyroidism of pituitary origin, without any increase in S-TSH, had a significantly elevated S-T3/S-T4 ratio. In subjects taking thyroxine, S-T4 but not S-T3 increased with the dose of thyroxine, leading to decreasing S-T3/S-T4 ratios. This indicates a mechanism that keeps S-T3 within normal limits also when the S-T4 supply is high. This applied also to athyreotic subjects on thyroxine and to subjects on thyroxine plus carbimazole, suggesting that the mechanism is independent of thyroid tissue, uninfluenced by carbimazole, and probably operates via the peripheral metabolism of T4. Changes in the S-T3/S-T4 ratio can be achieved by several mechanisms, and the specificity of ratio changes is low. However, by investigating the ratio S-T3/S-T4 in selected clinical states we can depict the ability of the organism to protect its normal S-T3 level in situations with divergent S-T4 concentrations, even if details about the mechanisms cannot be explained. SN - 0391-4097 UR - https://www.unboundmedicine.com/medline/citation/3794185/Thyroid_hormone_metabolism_in_thyroid_disease_as_reflected_by_the_ratio_of_serum_triiodothyronine_to_thyroxine_ L2 - https://link.springer.com/article/10.1007/BF03346952 DB - PRIME DP - Unbound Medicine ER -