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Variable thyrotropin response to thyrotropin-releasing hormone after small decreases in plasma free thyroid hormone concentrations in patients with nonthyroidal diseases.
J Clin Invest. 1980 Sep; 66(3):451-6.JCI

Abstract

Although a normal serum thyrotropin (TSH) concentration is generally considered to be the most important finding to support the clinical impression of euthyroidism in patients with nonthyroidal diseases and decreased serum triiodothyronine (T(3)), the regulation of TSH secretion in sick patients has not been studied previously. Accordingly, we studied the regulation of TSH secretion in 23 patients with nonthyroidal diseases; 15 of the patients had decreased serum T(3). TSH regulation was studied by measuring the TSH response to injected thyrotropin-releasing hormone (TRH) before and after effecting a small decrease in serum thyroxine (T(4)) and/or T(3) concentrations by iodide treatment, 262 mg daily for 10 d. Iodide treatment significantly decreased (> 10%) the free T(4) index (FT(4)-I) and/or free T(3) index (FT(3)-I) in all patients. FT(4)-I values were correlated (0.611, P < 0.001), with free T(4) concentration determined by equilibrium dialysis. Despite decreased FT(4)-I and/or FT(3)-I after iodide treatment in all patients, the TSH response to TRH after iodide treatment was augmented in only 8 of 15 patients who had decreased serum T(3) (group 1) and in only 5 of 8 patients who had a normal serum T(3). Mean base-line TSH concentration was increased significantly (P < 0.05) from 0.9+/-0.1 to 1.5+/-0.3 muU/ml in group 1 only. Comparison of the mean TSH response to TRH showed that there was no significant difference between groups 1 and 2. Moreover, no significant difference in thyroidal parameters was observed between patients who had augmented TSH response to TRH after iodides and those who had either similar or decreased TSH response irrespective of the initial serum T(3). These studies show that an augmented TSH response to TRH in response to a small reduction in serum T(4) and T(3) concentration occurred in only 57% of the entire group of patients with nonthyroidal diseases and that the presence or absence of a normal TSH response to this stimulus did not seem to be related to the base-line serum T(3) concentration. Because an increase in serum TSH in response to decreased serum T(4) and T(3) did not occur in about one-half of patients with nonthyroidal diseases, normal serum TSH may not be a reliable index of the euthyroid state in these patients.

Authors

No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

6772675

Citation

Maturlo, S J., et al. "Variable Thyrotropin Response to Thyrotropin-releasing Hormone After Small Decreases in Plasma Free Thyroid Hormone Concentrations in Patients With Nonthyroidal Diseases." The Journal of Clinical Investigation, vol. 66, no. 3, 1980, pp. 451-6.
Maturlo SJ, Rosenbaum RL, Pan C, et al. Variable thyrotropin response to thyrotropin-releasing hormone after small decreases in plasma free thyroid hormone concentrations in patients with nonthyroidal diseases. J Clin Invest. 1980;66(3):451-6.
Maturlo, S. J., Rosenbaum, R. L., Pan, C., & Surks, M. I. (1980). Variable thyrotropin response to thyrotropin-releasing hormone after small decreases in plasma free thyroid hormone concentrations in patients with nonthyroidal diseases. The Journal of Clinical Investigation, 66(3), 451-6.
Maturlo SJ, et al. Variable Thyrotropin Response to Thyrotropin-releasing Hormone After Small Decreases in Plasma Free Thyroid Hormone Concentrations in Patients With Nonthyroidal Diseases. J Clin Invest. 1980;66(3):451-6. PubMed PMID: 6772675.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Variable thyrotropin response to thyrotropin-releasing hormone after small decreases in plasma free thyroid hormone concentrations in patients with nonthyroidal diseases. AU - Maturlo,S J, AU - Rosenbaum,R L, AU - Pan,C, AU - Surks,M I, PY - 1980/9/1/pubmed PY - 1980/9/1/medline PY - 1980/9/1/entrez SP - 451 EP - 6 JF - The Journal of clinical investigation JO - J Clin Invest VL - 66 IS - 3 N2 - Although a normal serum thyrotropin (TSH) concentration is generally considered to be the most important finding to support the clinical impression of euthyroidism in patients with nonthyroidal diseases and decreased serum triiodothyronine (T(3)), the regulation of TSH secretion in sick patients has not been studied previously. Accordingly, we studied the regulation of TSH secretion in 23 patients with nonthyroidal diseases; 15 of the patients had decreased serum T(3). TSH regulation was studied by measuring the TSH response to injected thyrotropin-releasing hormone (TRH) before and after effecting a small decrease in serum thyroxine (T(4)) and/or T(3) concentrations by iodide treatment, 262 mg daily for 10 d. Iodide treatment significantly decreased (> 10%) the free T(4) index (FT(4)-I) and/or free T(3) index (FT(3)-I) in all patients. FT(4)-I values were correlated (0.611, P < 0.001), with free T(4) concentration determined by equilibrium dialysis. Despite decreased FT(4)-I and/or FT(3)-I after iodide treatment in all patients, the TSH response to TRH after iodide treatment was augmented in only 8 of 15 patients who had decreased serum T(3) (group 1) and in only 5 of 8 patients who had a normal serum T(3). Mean base-line TSH concentration was increased significantly (P < 0.05) from 0.9+/-0.1 to 1.5+/-0.3 muU/ml in group 1 only. Comparison of the mean TSH response to TRH showed that there was no significant difference between groups 1 and 2. Moreover, no significant difference in thyroidal parameters was observed between patients who had augmented TSH response to TRH after iodides and those who had either similar or decreased TSH response irrespective of the initial serum T(3). These studies show that an augmented TSH response to TRH in response to a small reduction in serum T(4) and T(3) concentration occurred in only 57% of the entire group of patients with nonthyroidal diseases and that the presence or absence of a normal TSH response to this stimulus did not seem to be related to the base-line serum T(3) concentration. Because an increase in serum TSH in response to decreased serum T(4) and T(3) did not occur in about one-half of patients with nonthyroidal diseases, normal serum TSH may not be a reliable index of the euthyroid state in these patients. SN - 0021-9738 UR - https://www.unboundmedicine.com/medline/citation/6772675/Variable_thyrotropin_response_to_thyrotropin_releasing_hormone_after_small_decreases_in_plasma_free_thyroid_hormone_concentrations_in_patients_with_nonthyroidal_diseases_ DB - PRIME DP - Unbound Medicine ER -