Breakdown of Autonomously Functioning Thyroid Nodule Accompanied by Acromegaly After Octreotide Treatment

Abstract

Patients with acromegaly are at increased risk of developing certain tumors, including goiter and thyroid nodules, and occasionally autonomous thyroid nodules. A 53-year-old woman presented at our hospital with untreated acromegaly. She had typical physical features of acromegaly with pituitary adenoma, and thyrotoxicosis with thyroid-stimulating hormone suppression was also confirmed. Thyroid ultrasonography and scintigraphy showed an autonomously functioning thyroid nodule on her right lobe. Because her thyrotoxicosis was mild, she was initially treated with octreotide for acromegaly. However, 1 month after octreotide administration, she developed neck pain and fever with transient thyrotoxicosis. The blood flow around the nodule then decreased and the excess trapping of isotope detected by scintigraphy was reduced, followed by normalization of insulin-like growth factor-1 levels and thyroid function. This case suggests that octreotide may have unexpected effects on autonomous thyroid nodules. However, further studies are needed to determine the clinical course of autonomously functioning thyroid nodules, including thyroid function and tumor manifestations, during octreotide therapy.

Keywords: acromegaly; autonomously functioning thyroid nodule; pituitary adenoma; somatostatin analog; thyrotoxicosis.

Figure 1

(A) Magnetic resonance imaging showed a pituitary tumor demonstrated less enhancement than the normal pituitary gland after intravenous contrast administration with invasion of the right cavernous sinus. (B,C) Thyroid enhanced computed tomography and ultrasonography showed several nodules inside the thyroid gland, of which the largest located at the bottom of the right lobe contained a cystic component and high vascularity.

Figure 2

(A) High IGF-1 level and thyrotoxicosis with TSH suppression were confirmed on admission. One month after octreotide treatment, the patient developed neck pain and fever accompanied by transient thyroid hormone elevation. IGF-1 levels and thyroid function subsequently normalized under octreotide treatment. Thin arrows, daily octreotide injection (100 μg/day); bold arrows, monthly octreotide-LAR injection (20 mg/month). (B,C) Thyroid ultrasonography (US) showed the largest thyroid nodule in the right lobe (34.4 × 25.3 × 23.3 mm) with high vascularity and a cystic region. This nodule showed as excess trapping of isotope in technetium-99 m pertechnetate scintigraphy against a low background of the thyroid. (D,E) One month after octreotide long-acting release treatment, the patient developed right cervical pain and temporary worsening of thyrotoxicosis. At that point, the blood flow surrounding the nodule decreased and the accumulation shown by scintigraphy was reduced. (F) Four months after octreotide treatment, thyroid US showed that the autonomous thyroid nodule had shrunk (20.3 × 13.8 × 12.8 mm) and most of the cystic lesion had been reduced. Adm., administration day; X, first day of octreotide treatment; LAR, long-acting release.