The utility of thyroid nuclear imaging and other studies in the detection and treatment of underlying thyroid abnormalities in patients with endogenous subclinical thyrotoxicosis.
OBJECTIVE
Endogenous subclinical thyrotoxicosis is diagnosed when a patient who is not taking exogenous thyroid hormone has a suppressed level of thyroid-stimulating hormone with normal levels of the free thyroid hormones thyroxine and triiodothyronine and other known causes of a suppressed thyroid-stimulating hormone level have been excluded. Although such a condition is caused by underlying thyroid disease, the specific nature and relative prevalence of these disorders and the utility of nuclear imaging and other studies in their detection remains unclear.


METHODS
The authors performed a retrospective study of 50 patients with endogenous subclinical thyrotoxicosis. The results of the history and physical examination, thyroid nuclear scan, radioactive iodine uptake measurement, and thyroid antibody studies were reviewed. The results of the nuclear imaging and thyroid antibody studies were combined in an attempt to establish an underlying diagnosis for each patient.


RESULTS
The thyroid nuclear imaging and antibody studies were used to establish a specific thyroid disorder in most of the patients (n = 39). These disorders included most commonly toxic multinodular goiter, various forms of autoimmune thyroid disease, and solitary toxic adenoma. A specific diagnosis was not determined in 11 patients. Therapy with I-131 radioactive iodine was administered to 14 of these patients, 13 of whom subsequently achieved a normal thyroid-stimulating hormone level.


CONCLUSIONS
Most patients with endogenous subclinical thyrotoxicosis have underlying thyroid abnormalities that can be determined by nuclear imaging and, in selected cases, thyroid antibody studies.
Tollin
S R
SR
Department of Medicine, University Hospital and the State University of New York at Stony Brook School of Medicine, Mineola, USA. SRTollin@aol.com
Fallon
E F
EF
Mikhail
M
M
Goldstein
H
H
Yung
E
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001323:Autoantibodies / Q000097:blood; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D013959:Thyroid Diseases / Q000097:blood / Q000000981:diagnostic imaging / Q000532:radiotherapy; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000276:immunology; D013971:Thyrotoxicosis / Q000097:blood / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
D001323:Autoantibodies; D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine