GOSERELIN INHIBITING UPTAKE ON SODIUM PERTECHNETATE TC-99M THYROID SCAN: A CASE REPORT

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Y.A. Onimode^1,2, O.O. Oyeyiola¹

1. Department of Nuclear Medicine, University College Hospital, Ibadan, Oyo State, Nigeria.
2. Department of Nuclear Medicine, College of Medicine, University of Ibadan, Ibadan, Oyo State, Nigeria.

Abstract

Introduction: Thyroiditis may be induced by goserelin (a long acting analogue of gonadotropin – releasing hormone) prescribed for the treatment of pain and bleeding of endometriosis. Goserelin induced thyroiditis has a possibility of affecting thyroid function and hence may cause poor uptake on sodiumpertechnetate Tc-99m thyroid scan.

Case presentation: This case report highlights a rare instance of a middleaged woman with symptomatic toxic goitre whose sodium pertechnetate Tc99m thyroid scan uptake was inhibited by goserelin therapy. Conclusion: Medical personnel caring for patients on goserelin need to be aware of the possibility of it affecting thyroid function.

Keywords: Goserelin, GnRH agonist, Thyroid gland, Sodium pertechnetate Tc99m, Endometriosis, Case report

Introduction

Goserelin is a long-acting analogue of gonadotropinreleasing hormone (GnRH) which inhibits secretion of gonadotropin from the pituitary gland.¹ It does this by reversible suppression of the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary gland.² The GnRH analogue has a greater affinity for its receptor, as high as 10-20 times.^3,4 As a treatment for endometriosis, it thins out the endometrial lining prior to ablative therapy, and relieves pain and bleeding.⁵ Few cases of goserelin-induced thyroiditis have been published in medical literature. We present a report of a sodium pertechnetate Tc-99m thyroid scan with uptake inhibited by goserelin.

CASE PRESENTATION
A 42-year old woman presented to our department with a two-year history of symptomatic toxic goitre. She had bilateral proptosis, hyperhidrosis, heat intolerance, menstrual irregularity, weight loss despite hyperphagia and increased appetite, and more recently, hoarseness. She had no history of excessive consumption of goitrogens. She had however grown up in a mountainous region of the country. Her main clinical findings were bilateral proptosis, goitre, with no tracheal deviation, retrosternal extension nor palpably enlarged regional cervical lymph nodes. There were no scalp swellings. She also had tachycardia of 96/min although her blood pressure was normal at 120/70 mmHg. An assessment of Graves’ disease with thyroid-associated ophthalmopathy was made. Prior to her presentation, she had been commenced on oral carbimazole 20 mg twice daily and atenolol 25 mg daily. Her thyroid function test result, which had been done two weeks prior to her presentation, was consistent with primary hyperthyroidism (see Table 1). Neck ultrasound showed diffusely enlarged thyroid lobes, with heterogeneous echotexture and minimal flow on colour Doppler interrogation. A solitary sub-centimetre hypoechoic nodule was seen in the left lobe which showed moderate flow on colour interrogation. The left lobe was larger than the right (15.0 cm3 and 11.9 cm3, respectively) resulting in a combined volume of 26.9 cm3. The overall impression was diffuse goitre with a solitary left thyroid nodule.