J Korean Soc Endocrinol.  2006 Feb;21(1):63-67. 10.3803/jkes.2006.21.1.63.

A Case of Iodine-induced Thyrotoxicosis with Acromegaly

Affiliations
  • 1Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.

Abstract

Hyperthyroidism is seen in 3.5-26% of subjects with acromegaly. Hyperthyroidism can be developed by thyroid stimulating hormone (TSH) dependent mechanism in TSH-secreting adenomas with acromegaly or by TSH independent mechanism through the stimulation of thyroid cells by growth hormone (GH). So, confirming the cause of hyperthyroidism is important to treat that. We report a case of a 56-year-old man who had acromegaly with iodine-induced thyrotoxicosis. He took the sea tangle for 4 years because he had constipation. His face and hands indicated acromegaly. Thyroid function test showed that T3 and free T4 were increased and TSH was decreased. Ultrasonography of neck showed diffuse enlargement of thyroid gland and thyroid scan showed decreased uptake of thyroid gland. So we could confirm iodine-induced thyrotoxicosis due to excessive iodine intake. Serum GH and insulin-like growth factor (IGF)-1 were markedly increased and brain MRI showed heterogenous 1 cm sized pituitary mass in right side. Acromegaly was confirmed by brain MRI, pituitary stimulation test and increased level of GH, IGF-1. He stopped iodine intake. After 6 months, T3, free T4 and TSH were normalized and he is waiting for the surgical removal of pituitary adenoma.


MeSH Terms

Acromegaly*
Adenoma
Brain
Constipation
Growth Hormone
Hand
Humans
Hyperthyroidism
Insulin-Like Growth Factor I
Iodine
Magnetic Resonance Imaging
Middle Aged
Neck
Pituitary Neoplasms
Thyroid Function Tests
Thyroid Gland
Thyrotoxicosis*
Thyrotropin
Ultrasonography
Growth Hormone
Insulin-Like Growth Factor I
Iodine
Thyrotropin

Figure

  • Fig. 1 About 1 cm sized oval shaped heterogeneous signal intensity lesion along the right side pituitary gland with asymmetrical right side convex margined upper margin with slightly left located infundibulum. (A) coronal view, (B) sagittal view.

  • Fig. 2 Neck sonography shows a diffuse enlarged thyroid that has heterogeneous echotexture and multiple anechoic cystic lesion below 0.5 cm sized.

  • Fig. 3 (A) After injection of Tc-99m pertechnetate 5 mci, the decreased uptake of Tc-99m is noted with front visualization of thyroidal activity. (B) The uptake ratio of I-131 at 2 hours and the uptake ratio of Tc-99m pertechnetate at 20 minutes are measured 0.97% and 0.63%, respectively.


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