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A patient with widely fluctuating thyroid-stimulating hormone measurements.

CASE DESCRIPTION

A 56-year-old man had a thyroid-stimulating hormone (TSH)4 value of 22.5 [micro]IU/mL (reference interval 0.4-4.6 [micro]IU/mL). The increased TSH prompted review of his previous thyroid testing results (Table 1). The patient's history revealed a diagnosis of papillary thyroid carcinoma 8 months prior, which was treated with total thyroidectomy and [sup.131]I radioablation followed by L-thyroxine (Synthroid) treatment. This was his first follow-up visit for evaluation of recurrence of his disease.

QUESTIONS

1. What is done to patients to enhance [sup.131]I uptake?

2. What is the target TSH concentration on the day of [sup.131]I administration?

ANSWERS

Radioiodine ([sup.131]I) is used for radioablation of thyroid remnants (1), as was done on March 12, 2012 for our patient, and to scan for recurrence of thyroid cancer (2), as was done on November 2, 2012. Increased TSH, achieved by withholding thyroid supplements or injecting recombinant human TSH (rhTSH), enhances [sup.131]I uptake (3, 4) that, in turn, will increase the sensitivity of whole body scan for residual or recurrent thyroid cancer. Two doses of 0.9 mg rhTSH, 24 hours apart, are optimal to achieve peak TSH concentrations of 60-240 [micro]IU/mL 24 h after the second dose, and to maintain a 25-30 [micro]IU/mL therapeutic concentration on the day of [sup.131]I administration (4, 5). The increased TSH concentration was due in our patient to 2 injections of rhTSH on the days prior to the laboratory testing. Although the measured TSH concentration (22.5 [micro]IU/mL) was slightly lower than desired, whole body radioiodine scan was performed, and it did not disclose signs of recurrence.

Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, oranalysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.

Authors' Disclosures or Potential Conflicts of Interest: No authors declared any potential conflicts of interest.

References

(1.) Barbaro D, Boni G. Radioiodine ablation of post-surgical thyroid remnants after preparation with recombinant human TSH: why, how and when. Eur J Surg Oncol 2007; 33:535-40.

(2.) Pacini F, Castagna MG. Diagnostic and therapeutic use of recombinant human TSH (rhTSH) in differentiated thyroid cancer. Best Pract Res Clin Endocrinol Metab 2008; 22:1009-21.

(3.) Tala H, Robbins R, Fagin JA, Larson SM, Tuttle RM. Five-yearsurvival issimilar in thyroid cancer patients with distant metastases prepared for radioactive iodine therapy with either thyroid hormone withdrawal or recombinant human TSH. J Clin Endocrinol Metab 2011; 96:2105-11.

(4.) Pacini F, Molinaro E, Castagna MG, Lippi F, Ceccarelli C, Agate L, et al. Ablation of thyroid residues with 30 mci (131)I:a comparison in thyroid cancer patients prepared with recombinant human TSH or thyroid hormone withdrawal. J Clin Endocrinol Metab 2002; 87:4063-8.

(5.) Mariani G, Ferdeghini M, Augeri C, Villa G, Taddei GZ, Scopinaro G, et al. Clinical experience with recombinant human thyrotrophin (rhTSH) in the management of patients with differentiated thyroid cancer. Cancer Biother Radiopharm 2000; 15:211-7.

Received October 30, 2013; accepted January 13, 2014.

DOI: 10.1373/clinchem.2013.218164

Micah D. Will [1,2,3]and Geza S. Bodor [1,2]

* Address correspondence to this author at: VA ECHCS, P & LMS 113, 1055 Clermont St., Denver, CO 80220; e-mail gsbodor@comcast.net.

[1] Pathology and Laboratory Medicine Service, VA Eastern Colorado Health Care System, Denver, CO; [2] Department of Pathology, University of Colorado Denver, Denver, CO; [3] current affiliation: Department of Pathology and Area Laboratory Services, Brooke Army Medical Center, San Antonio, TX.

[4] Nonstandard abbreviations: TSH, thyroid-stimulating hormone; rhTSH, recombinant human TSH.
Table 1. Previous thyroid testing results.

Date of sample       TSH, [micro]IU/mL        Thyroxine,
collection          (reference interval,     [micro]g/dL
                          0.4-4.6)            (reference
                                           interval, 4.5-12)

11/2/2012                   22.5                 15.9
10/16/2012                  0.1                  13.0
7/27/2012                   0.5
5/9/2012                    0.2

3/12/2012, Thyroid
ablation performed

3/12/2012                   32.1                  0.4
11/14/2011
10/11/2011                  0.5
7/21/2011                   0.2
7/5/2011
4/21/2011                   1.4                   8.7
2/5/2010                    1.6

Date of sample      Free thyroxine,     Thyroglobulin,
collection          ng/dL (reference   ng/mL (reference
                       interval,       interval, 0.5-55)
                       1.00-1.85)

11/2/2012                 1.82               <0.5
10/16/2012                1.43
7/27/2012
5/9/2012                  1.29               <0.5

3/12/2012, Thyroid
ablation performed

3/12/2012                                    <0.5
11/14/2011                                   <0.5
10/11/2011                                    (a)
7/21/2011
7/5/2011
4/21/2011                 0.69               21.2
2/5/2010

Date of sample      Thyroglobulin
collection          antibody, IU/mL
                      (reference
                    interval, 0-40)

11/2/2012                 <20
10/16/2012
7/27/2012
5/9/2012                  <20

3/12/2012, Thyroid
ablation performed

3/12/2012                 <20
11/14/2011                <20
10/11/2011                <20
7/21/2011
7/5/2011                  <20
4/21/2011                 <20
2/5/2010

(a) Insufficient sample volume for testing.
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Article Details
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Title Annotation:What Is Your Guess?
Author:Will, Micah D.; Bodor, Geza S.
Publication:Clinical Chemistry
Article Type:Clinical report
Date:Oct 1, 2014
Words:865
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