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Continuing medical education
Thyroid: take the test!
Thyroid function is best evaluated by measuring the serum TSH. Its assay is far more precise and sensitive than measuring free T4 (thyroxine), which is usually quantified by estimate rather than measure. Free T4 is useful when following an acute case of hyperthyroidism, as well as central or pituitary hypo thyroidism. When substituting patients with levothyroxine, many factors should be considered in the interpretation of TSH levels. Of prime importance is the timing of TSH measurement relative to the beginning of treatment. Also many supplements, foods and clinical conditions can decrease levothyroxine absorption and therefore modify TSH values. Three main antibodies can also be measured to help establish a diagnosis, but when their results are positive, there is no need for rerun. In the evaluation of hyper thyroidism, thyroid scintigraphy is the most useful diagnostic imaging test, and it allows differentiating between the various causes. However, thyroid sonography is not as helpful but proves to be the best test in the evaluation of thyroid nodules. Inversely, scintigraphy should not be used to diagnose nodules in euthyroid subjects. Read more in French
Subclinical thyroid dysfunction: when a little becomes enough...
Subclinical thyroid dysfunctions consist of abnormal values of thyroid-stimulating hormone (TSH) – elevated in the case of subclinical hypothyroidism – combined with normal range values of free thyroxine (T4) and triiodothyronine (T3). Each year, 2% to 5% of patients with subclinical hypothyroidism will evolve towards overt hypothyroidism. Progression rate to hypothyroidism is in proportion with initial TSH level, and is more important when antithyroid antibodies are positive. Even though treatment often remains a dilemma, it seems appropriate to treat symptomatic patients, as well as pregnant and infertile women, patients at risk of cardiovascular disease and when a goiter and antithyroid antibodies are present because these specific dysfunctions are reversible. Pregnancy, for its part, is a particular chapter of subclinical hypothyroidism. First trimester TSH level should be 2.5 mIU/L or less. Read more In French
When the thyroid loses control
Hyperthyroidism, a frequent disease in young women, can have numerous manifestations due to the ubiquitous distribution of thyroid hormone receptors. Even though symptoms and clinical signs usually correlate with the levels of thyroid hormones, their perception and tolerance vary with each individual. The present article reviews the most common symptoms and causes of hyperthyroidism. Diagnosis and treatment strategies such as antithyroid medication, radioactive iodine and surgery are discussed. An algorithm for the initial investigation of hyperthyroidism is also proposed. Read more in French
Great mimickers: thyroid emergencies in the resuscitation room!
The thyroid is notable for its impact on most other organs in the body. An unbalanced thyroid function can easily mislead us in many other directions. This article reviews three emergent thyroid-born pathologies. Thyroid storms are first reviewed, with an emphasis on treating all cases of hyperthyroidism as having the potential to evolve into a thyroid storm until hormones have normalized. Myxedema crises should always be considered when faced with an identifiable precipitating factor with a combination of shiverless hypothermia and altered sensorium. Compressive goiters that compromise breathing are surgical emergencies, and their identification should prompt urgent referral to an anaesthesiologist. Initial treatment in the resuscitation room is detailed for all pathologies. Read more in French
Thyroid nodule – taking the appropriate decision
Taking charge of thyroid nodules is a common clinical occurrence for which practice guidelines exist. Approximately 10% of nodules are malignant lesions. Risk of cancer is the same whether in the presence of a simple nodule or multinodular goiter. Anamnesis and physical exam are the first elements that will help identify patients at high or low-risk of malignancy. TSH measurement and thyroid ultrasound are the means to determine if a biopsy should be practiced. Ultra - sound also enables selection of nodules that should be biopsied using criteria other than size only. Fine needle aspiration is an efficient diagnostic act. When a nodule is benign and stable, clinical follow-up and ultrasound are sufficient. Surgery is indicated when nodule is suspect or when malignant, when it grows or when patient experiences compression symptoms .Read more in French
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