Endocrine Abstracts

A 22-year-old Caucasian female was referred to thyroid specialist clinic due to difficulties fully suppressing her thyroid stimulating hormone (TSH) despite high dose combination therapy of triiodothyronine (T3) and thyroxine (T4) treatment. She had a well-differentiated thyroid -carcinoma of left thyroid lobe treated with left lobectomy. Several other small primary thyroid carcinoma lesions were detected on further examination of the histology which lead to completion thyroidectomy and radioiodine treatment.

On assessment, she denied any symptoms of dysthyroidism. Her great-grandmother had goitre; otherwise there is no other evidence of thyroid disease in the family. Clinically, she was euthyroid with no evidence of recurrence or lymphadenopathy. Anterior pituitary function tests were all within normal range and MRI scan of pituitary gland indicated a 30-mm macroadenoma. Thyroid function tests showed free T4 of 29.8 pmol/l (10–22 pmol/l), free T3 of 10.7 pmol/l (3.1–6.8 pmol/l) and a TSH of 0.06 mU/l (0.3–4.5 mmol/l). Her thyroglobulin level was undetectable. Following evaluation, she was diagnosed with biochemical hyperthyroidism and likely pituitary incidentaloma and was advised to discontinue treatment with T3 to prevent thyrotoxic effects.

On follow-up, patient was pregnant; otherwise clinically unremarkable. However, her pituitary mass had grown and was abutting the optic chiasm. Thyroglobulin remained undetectable. The tumour growth was attributed to pregnancy changes and patient was managed in joint obstetric and endocrine clinic. Post-partum scans showed macroadenoma with no change in size. Thyroglobulin remained undetectable and alpha sub-unit was low. However, TSH remained at detectable range. Patient did not wish to undergo possible curative surgery as it may affect her chance of future pregnancies. Following multi-disciplinary team discussion, somatostatin analogue was trialled. TSH level supressed to undetectable range with somatostatin; however, tumour size did not change. Currently, patient is managed on a combination of T4 and somatostatin analogue under close follow-up.