What’s in the web for family physicians – Thyroid disorders

Wilbert WB Wong 王維斌，Alfred KY Tang 鄧權恩

HK Pract 2019;41:111-112

Thyroid dysfunction or thyroid nodules are problems commonly encountered by family physicians. It would be useful for family physicians to be familiarised with the topic.

Consequence of excess iodine

Iodine is a micronutrient essential for the production of thyroid hormones. The primary source of dietary iodine includes consumption of iodine fortified food, like salt, dairy products and bread, and food which are naturally abundant in the micronutrient, such as seafood. Recommended daily iodine intake is 150 μg for adults who are not pregnant or lactating. Ingestion of iodine in excess or exposure above this threshold is generally well-tolerated. However, with susceptible individuals, including those with pre-existing thyroid disease, the risk of developing iodine-induced thyroid dysfunction might be increased.

The article publishes a list of food items rich in iodine which can be helpful for patients with hyperthyroidism to avoid them, or, patients with hypothyroidism to be more aware of them to ensure an adequate intake.

Iodine contents in different types of food

The UK Iodine Group is a group of experts in iodine nutrition, thyroid disease and public health, to promote awareness of the importance of iodine in diet and to make evidence-based recommendations with the aim to eradicate iodine deficiency in UK. Dietary recommendations to pregnancy women and iodine contents in different types of food are available at the website for reference.

Guidelines on managing hyperthyroidism and other causes of thyrotoxicosis

New evidence-based recommendations from the American Thyroid Association (ATA) provide guidance to clinicians on the management of patients with different forms of thyrotoxicosis, including hyperthyroidism. Appropriate treatment of thyrotoxicosis requires accurate diagnosis, and there were 124 recommendations presented in the 2016 Guidelines to define current best practices on patient evaluation, diagnosis, and treatment. The recommendations also cover areas on management of different types of thyroid diseases, how to handle thyrotoxicosis in pregnancy, and how to select and implement the various treatment options such as surgery, radioactivity, and the use of antithyroid drugs.

Guidelines on diagnosis and management of thyroid nodules

The Guidelines were published by The American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi Medical Guidelines in 2016. With the incorporation of recent scientific evidence, it is an updated edition covering the use of new diagnostic tools and treatments, with emphasis on avoiding unnecessary diagnostic procedures and risk of medical or surgical over-treatment. The importance of adequate patient information and participation in clinical decision making, together with the role of a multidisciplinary approach to thyroid nodular disease are fully discussed.

The key issues covered in these guidelines are: (1) US-based categorisation of the malignancy risk and indications for US-guided FNA (henceforth, FNA), (2) cytologic classification of FNA samples, (3) the roles of immunocytochemistry and molecular testing applied to thyroid FNA, (4) therapeutic options, and (5) follow-up strategy.

Guidelines on managing Graves’ disease

This latest guideline in 2018 is developed by European Thyroid Association on the management of Graves’ Hyperthyroidism.

Graves’ disease (GD) is a systemic autoimmune disorder characterised by the infiltration of thyroid antigen-specif ic T cells into thy roid-stimulating hormone receptor (TSH-R) - expressing tissues. Stimulatory autoantibodies (Ab) in GD activate the TSH-R leading to thyroid hyperplasia and unregulated thyroid hormone production and secretion.

Diagnosis of GD is straightforward in a patient with biochemically confirmed thyrotoxicosis, positive TSH-R-Ab, a hypervascular and hypoechoic thyroid gland (ultrasound), and associated orbitopathy.

In GD, measurement of TSH-R-Ab is recommended for an accurate diagnosis/differential diagnosis, prior to stopping antithyroid drug (ATD) treatment and during pregnancy.

Graves’ hyperthyroidism is treated by decreasing thyroid hormone synthesis with the use of ATD, or by reducing the amount of thyroid tissue with radioactive iodine (RAI) treatment or total thyroidectomy.

Management of hypothyroidism

The Guideline is prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. The main purpose of the Guideline is to review the goals of levothyroxine therapy, the optimal prescription of conventional levothyroxine therapy, the sources of dissatisfaction on levothyroxine therapy, the evidence on treatment alternatives, and the relevant knowledge gaps.

Management of thyroid eye disease

Thyroid eye disease (TED) is the most common orbital disorder in adults worldwide. It is also the most common cause of unilateral or bilateral axial proptosis (exophthalmos), acquired strabismus or lid retraction. The reported risk factors for the development of TED include male gender, older age at onset (>50 years), smoking, use of radioactive iodine (RAI), and postablative hypothyroidism. Smoking cessation and early stabilisation of thyroid function are the most important measures on primary and secondary TED prevention.

Radioactive iodine treatment for hyperthyroidism

Radioiodine therapy is treatment of hyperthyroidism with the use of nuclear medicine, which can also be used to treat thyroid cancer. When a small dose of radioactive iodine I-131 isotope is swallowed, it is absorbed into the bloodstream and concentrated by the thyroid gland, where it starts to destroy cells of the thyroid gland. This article includes a video presentation on how the treatment is given, what could the patient experience be with the therapy, and precautions needed with the treatment.