Endocrine Abstracts

Introduction: McCune Albright syndrome (MAS) is a rare, sporadic disease that affects the skin, skeleton and several endocrine systems, caused by an activating mutation in the GNAS gene that leads to endocrine cell hyperfunction and increased cell proliferation. The development of thyroid carcinoma in MAS is considered an uncommon event and, on the other hand, it is well established that acromegaly is associated with an increased prevalence of malignant tumors including thyroid cancer.

Clínical case: A 53-year-old female without family history of endocrine disease, surgically treated for facial asymmetry, was diagnosed in 1992 with polyostotic fibrous dysplasia, GH/prolactin producing pituitary macroadenoma and toxic multinodular goiter. Hyperprolactinemia and hyperthyroidism were controlled from the diagnosis with dopamine agonists and methimazole, but acromegaly remained active until 1999 because the patient refused treatment with subcutaneous octreotide. In January 2000 intramuscular Sandostatin LAR 30 mg/month was included in the treatment. In 2007 Sandostatin was replaced by subcutaneous GH receptor antagonist Pegvisomant, 20 mg/day because the control objective for IGF-1 was not achieved. Later, after confirming a significant increase in the size of the pituitary adenoma in magnetic resonance, we opted for combined therapy with Sandostatin LAR and Pegvisomant. Since then, the macroadenoma remains stable and IGF-1, PRL, and thyroid function are normal. In the follow-up thyroid ultrasonography (US) performed in 2017, several nodules in the left lobe thyroid suspected of papillary carcinoma were described and fine-needle aspiration (FNA) of the larger nodule was compatible with papillary thyroid carcinoma (PTC). In June 2017, total thyroidectomy was performed and the histopathological report confirmed the presence of a bilateral multifocal papillary carcinoma with extension to the extrathyroidal tissue adjacent to the left thyroid lobe, associated with nodular hyperplasia and chronic lymphocytic thyroiditis. Radioactive iodine ablation was performed 1 month later and the total body scan performed after treatment did not show evidence of metastasis. Serum thyroglobulin remains undetectable.

Discussion: Several studies report a high frequency of PTC in acromegalic patients, especially in those with prolonged periods of uncontrolled acromegaly, although the controversy remains regarding its BRAF mutation dependence. Previous data suggest relative aggressiveness of these tumours but the outcome seems good after surgery and I-131 therapy. In this patient, the sustained exposure to an overactive GH/IGF axis may have played a dominant role in the development of PTC. Acromegalic patients should be routinely screened by thyroid US and undergo FNA according to current criteria.