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The dynamic pituitary response to escalating-dose TRH stimulation test in hypothyroid patients treated with liothyronine or levothyroxine replacement therapy.
J Clin Endocrinol Metab. 2013 May; 98(5):E862-6.JC

Abstract

CONTEXT

A recent trial showed that 1:3 μg:μg liothyronine (L-T3) substitution for levothyroxine (L-T4) achieving near-identical TSH levels resulted in a significant decrease in weight and cholesterol levels with no appreciable changes in cardiovascular parameters, suggesting a differential peripheral response to the therapy.

OBJECTIVE

We characterized the pituitary-thyroid axis in hypothyroid patients receiving equivalent doses of L-T3 or L-T4 by escalating-dose TRH stimulation test.

DESIGN

A secondary analysis of a L-T3 vs L-T4 therapy trial was performed.

SETTING

The study was conducted at the National Institutes of Health.

PATIENTS

Thirteen patients were studied.

INTERVENTIONS

Escalating-dose (5, 15, and 200 μg) TRH stimulation test on both treatment arms.

MAIN OUTCOME MEASURES

Study outcomes were peak serum TSH concentration (Cmax), time to peak TSH concentration (Tmax), area under the curve from 0 to 60 minutes (AUC₀₋₆₀) after TRH injection.

RESULTS

Thirteen patients aged 51.2 ± 8.29 years completed escalating-dose TRH stimulation test. No significant difference between L-T3 and L-T4 treatments was observed in TSH Cmax or area under the curve. L-T4 resulted in a small but significantly shorter Tmax compared to L-T3 (3.5 ± 0.73 min on 200 μg TRH dose, P < .03). In addition, 5 μg TRH dose compared to 200 μg resulted in a shorter Tmax on both treatment arms (6.9 ± 0.59 min L-T3, 4 ± 0.3 min L-T4; P = .0002).

CONCLUSIONS

The assessment of the dynamic pituitary response to escalating doses of TRH confirms that substitution of L-T3 for L-T4 on a 1:3 ratio achieves a near-identical degree of pituitary euthyroidism. Furthermore, the data suggest that lower doses of TRH might provide clinically relevant information of thyrotroph function, particularly when investigating partial pituitary insufficiency states.

Authors+Show Affiliations

Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892-1613, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Comparative Study
Journal Article
Randomized Controlled Trial
Research Support, N.I.H., Extramural
Research Support, N.I.H., Intramural

Language

eng

PubMed ID

23585666

Citation

Yavuz, Sahzene, et al. "The Dynamic Pituitary Response to Escalating-dose TRH Stimulation Test in Hypothyroid Patients Treated With Liothyronine or Levothyroxine Replacement Therapy." The Journal of Clinical Endocrinology and Metabolism, vol. 98, no. 5, 2013, pp. E862-6.
Yavuz S, Linderman JD, Smith S, et al. The dynamic pituitary response to escalating-dose TRH stimulation test in hypothyroid patients treated with liothyronine or levothyroxine replacement therapy. J Clin Endocrinol Metab. 2013;98(5):E862-6.
Yavuz, S., Linderman, J. D., Smith, S., Zhao, X., Pucino, F., & Celi, F. S. (2013). The dynamic pituitary response to escalating-dose TRH stimulation test in hypothyroid patients treated with liothyronine or levothyroxine replacement therapy. The Journal of Clinical Endocrinology and Metabolism, 98(5), E862-6. https://doi.org/10.1210/jc.2012-4196
Yavuz S, et al. The Dynamic Pituitary Response to Escalating-dose TRH Stimulation Test in Hypothyroid Patients Treated With Liothyronine or Levothyroxine Replacement Therapy. J Clin Endocrinol Metab. 2013;98(5):E862-6. PubMed PMID: 23585666.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The dynamic pituitary response to escalating-dose TRH stimulation test in hypothyroid patients treated with liothyronine or levothyroxine replacement therapy. AU - Yavuz,Sahzene, AU - Linderman,Joyce D, AU - Smith,Sheila, AU - Zhao,Xiongce, AU - Pucino,Frank, AU - Celi,Francesco S, Y1 - 2013/04/12/ PY - 2013/4/16/entrez PY - 2013/4/16/pubmed PY - 2013/7/6/medline SP - E862 EP - 6 JF - The Journal of clinical endocrinology and metabolism JO - J Clin Endocrinol Metab VL - 98 IS - 5 N2 - CONTEXT: A recent trial showed that 1:3 μg:μg liothyronine (L-T3) substitution for levothyroxine (L-T4) achieving near-identical TSH levels resulted in a significant decrease in weight and cholesterol levels with no appreciable changes in cardiovascular parameters, suggesting a differential peripheral response to the therapy. OBJECTIVE: We characterized the pituitary-thyroid axis in hypothyroid patients receiving equivalent doses of L-T3 or L-T4 by escalating-dose TRH stimulation test. DESIGN: A secondary analysis of a L-T3 vs L-T4 therapy trial was performed. SETTING: The study was conducted at the National Institutes of Health. PATIENTS: Thirteen patients were studied. INTERVENTIONS: Escalating-dose (5, 15, and 200 μg) TRH stimulation test on both treatment arms. MAIN OUTCOME MEASURES: Study outcomes were peak serum TSH concentration (Cmax), time to peak TSH concentration (Tmax), area under the curve from 0 to 60 minutes (AUC₀₋₆₀) after TRH injection. RESULTS: Thirteen patients aged 51.2 ± 8.29 years completed escalating-dose TRH stimulation test. No significant difference between L-T3 and L-T4 treatments was observed in TSH Cmax or area under the curve. L-T4 resulted in a small but significantly shorter Tmax compared to L-T3 (3.5 ± 0.73 min on 200 μg TRH dose, P < .03). In addition, 5 μg TRH dose compared to 200 μg resulted in a shorter Tmax on both treatment arms (6.9 ± 0.59 min L-T3, 4 ± 0.3 min L-T4; P = .0002). CONCLUSIONS: The assessment of the dynamic pituitary response to escalating doses of TRH confirms that substitution of L-T3 for L-T4 on a 1:3 ratio achieves a near-identical degree of pituitary euthyroidism. Furthermore, the data suggest that lower doses of TRH might provide clinically relevant information of thyrotroph function, particularly when investigating partial pituitary insufficiency states. SN - 1945-7197 UR - https://www.unboundmedicine.com/medline/citation/23585666/The_dynamic_pituitary_response_to_escalating_dose_TRH_stimulation_test_in_hypothyroid_patients_treated_with_liothyronine_or_levothyroxine_replacement_therapy_ L2 - https://academic.oup.com/jcem/article-lookup/doi/10.1210/jc.2012-4196 DB - PRIME DP - Unbound Medicine ER -