123I thyroid uptake and thyroid size at 24, 48, and 72 hours after the administration of recombinant human thyroid-stimulating hormone to normal volunteers.
BACKGROUND
Recombinant human TSH (rhTSH) is used to evaluate thyroid carcinoma patients and off-label for (131)I thyroid ablation and nontoxic goiter therapy.


OBJECTIVE
Our objective was to determine the optimal time for (131)I administration after rhTSH.


METHODS
Twenty-five euthyroid nongoitrous volunteers participated in the study.


METHODS
Baseline 24-h thyroid (123)I uptake (RAIU) was measured, and then 0.1 mg rhTSH was administered. (123)I was administered 24, 48, or 72 h after rhTSH, and a repeat 24-h RAIU was obtained.


METHODS
The study was conducted at an academic research center.


METHODS
Thyroid function tests, thyroid ultrasounds, and electrocardiograms were measured before rhTSH, then daily for 4 d, and finally 7 d after rhTSH.


RESULTS
Serum TSH concentrations 24 h after rhTSH increased from 1.7 +/- 0.5 muU/ml (mean +/- sd) to 13.3 +/- 4. The 24-h RAIUs rose from 25 +/- 5 to 47 +/- 8% (88% increase) when the (123)I was given at 24 h after rhTSH and from 29.8 +/- 7 to 40.5 +/- 13% (36% increase) when the (123)I was given at 48 h and were unchanged when the (123)I was given at 72 h. The post-rhTSH RAIU increase was greater at 24 than at 72 h (P < 0.005) and marginally greater than at 48 h (P = 0.057). Thyroid volumes significantly increased 48 h after rhTSH (10 +/- 3.8 vs. 11.1 +/- 3.7 ml; P < 0.009). Electrocardiograms were normal.


CONCLUSIONS
Marked increases in RAIU occurred when (123)I was given 24 h after rhTSH administration to euthyroid volunteers. Smaller increases were observed at 48 h and none at 72 h.
Pena
Samara
S
Section of Endocrinology, Diabetes, and Nutrition, Boston University Medical Center, Evans 201, 88 East Newton Street, Boston, MA 02118, USA.
Arum
Seth
S
Cross
Mary
M
Magnani
Barbarajean
B
Pearce
Elizabeth N
EN
Oates
M Elizabeth
ME
Braverman
Lewis E
LE
D000328:Adult; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D009929:Organ Size / Q000187:drug effects; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000097:blood; D013954:Thyroglobulin / Q000097:blood; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000187:drug effects*; D013972:Thyrotropin / Q000008:administration & dosage* / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D014463:Ultrasonography
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D014284:Triiodothyronine; D013972:Thyrotropin; D013954:Thyroglobulin; D013974:Thyroxine