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Cited by 75Thyroid Disorders and TreatmentsThyroid and Parathyroid SurgeryOphthalmology and Eye Disorders

Pattern of recovery of the hypothalamic-pituitary-thyroid axis following radioactive iodine therapy in patients with Graves' disease

Uy, Harry L., Reasner, Charles A., Samuels, Mary H.·1995·The American Journal of Medicine
DOI 10.1016/s0002-9343(99)80137-5
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Abstract

Purpose To characterize the time course of recovery of the hypothalamic-pituitary-thyroid (HPT) axis by determining the frequency, onset, duration, and clinical attributes of the central hypothyroid phase following 131I therapy for Graves' disease and to examine whether the central hypothyroid phase is due to direct pituitary thyrotroph suppression or to hypothalamic thyrotropin-releasing hormone (TRH) deficiency.Patients and methods Twenty-one hyperthyroid patients with Graves' disease evaluated at a university endocrine clinic and treated with radioactive iodine were prospectively studied. Serial thyroid function levels (serum thyroxine [T4], free thyroxine [free T4], triiodothyronine [T3], and thyroid-stimulating hormone [TSH]) were measured and TRH stimulation tests were performed at 2 to 4 week intervals for all subjects following 131I treatment. None of the patients was treated with thionamides after receiving 131I therapy.Results Nineteen (90%) of the patients with Graves' disease experienced a transient central hypothyroid phase defined as the presence of a suppressed or inappropriately normal TSH level despite a low free T4 level following 131I treatment. This phase occurred a mean of 62.8 +/- 5.1 days following 131I treatment, persisted for an average of 24.7 +/- 2.4 days, and was not predictive of eventual treatment outcome. All patients had concordantly low T4 and T3 levels during this period and exhibited a blunted TSH response to TRH compared to 29 euthyroid control subjects, suggesting primary feedback suppression at the level of the pituitary thyrotrophs. The suppressed thyrotrophs required a minimum of 2 weeks to recover once patients became hypothyroid. The length of preexisting hyperthyroidism, basal free T4 elevation, and administered dose of 131I failed to predict the duration of the central hypothyroid phase, although a higher dose of 131I was associated with an earlier onset of central hypothyroidism (r = -.51, P < 0.05).Conclusions Clinicians should be aware of the delay in the recovery of the HPT axis that occurs in the majority of patients with Graves' disease treated with 131I and is manifested by a transient central hypothyroid phase. The blunted TSH response to TRH stimulation during this period suggests that suppression occurs primarily at the level of the pituitary thyrotrophs. The use of sensitive TSH measurements alone to monitor these patients during this period is not helpful and may be misleading.

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Authors
Uy, H. L., Reasner, C. A., & Samuels, M. H.
Affiliations
The University of Texas at San Antonio Health Science Center (US)
ORCID
Samuels, Mary H.
Venue
The American Journal of Medicine
Publisher
Elsevier BV
Published
1995-08
Volume
99
Issue
2
Pages
173-179
ISSN
0002-9343 (ISSN-L)
DOI
10.1016/s0002-9343(99)80137-5
OpenAlex
W2059422783
Cited by
75
References
29
Citations by year
2026: 3 · 2025: 2 · 2024: 1 · 2023: 2 · 2022: 3 · 2021: 2 · 2020: 3 · 2019: 2 · 2018: 4 · 2017: 1 · 2016: 4 · 2015: 2 · 2014: 4 · 2013: 4 · 2012: 2
FWCI
1.05
Type
journal article
Language
en
Open access
closed
Licence
Locations
  • The American Journal of Medicine (publishedVersion)
  • PubMed (publishedVersion)
Funders
National Institutes of Health
Topics
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Thyroid Disorders and Treatments
  • Health Sciences › Medicine › Surgery › Thyroid and Parathyroid Surgery
  • Health Sciences › Medicine › Pathology and Forensic Medicine › Ophthalmology and Eye Disorders
Keywords
Graves' disease, radioiodine therapy, central hypothyroidism, hypothalamic-pituitary-thyroid axis, thyrotropin-releasing hormone, thyroid-stimulating hormone, hyperthyroidism, iodine-131 dose, thyroid function recovery, TRH stimulation test, triiodothyronine, thyroxine
MeSH terms
Adult, Analysis of Variance, Female, Graves Disease, Humans, Hypothalamo-Hypophyseal System, Iodine Radioisotopes, Male, Middle Aged, Prospective Studies, Thyroid Gland, Thyroid Hormones, Treatment Outcome

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