Thyroid Hormone Measurements and Diagnostic Tests
27 Questions
2 Views
3.6 Stars

Thyroid Hormone Measurements and Diagnostic Tests

Created by
@SalutaryLight4722

Questions and Answers

What is the predominant secretory product?

T4

Which hormone has greater biological activity?

T3

What is the normal range for plasma T4 levels?

60-140nM

What is the normal range for plasma T3 levels?

<p>1.1-2.7nM</p> Signup and view all the answers

What are the clinical features of hyper and hypothyroidism?

<p>Some clinical features of hyperthyroidism include weight loss, increased appetite, heat intolerance, tremors, and palpitations. Clinical features of hypothyroidism include weight gain, fatigue, cold intolerance, constipation, and dry skin.</p> Signup and view all the answers

What are the causes of hyper and hypothyroidism?

<p>Hyperthyroidism can be caused by Graves' disease, toxic adenoma, and toxic multinodular goiter. Hypothyroidism can be caused by Hashimoto's thyroiditis, iodine deficiency, and certain medications.</p> Signup and view all the answers

Why are highly sensitive (new generation) assays required for TSH?

<p>Highly sensitive TSH assays are required to detect even small changes in TSH levels, as subtle alterations in TSH can indicate thyroid dysfunction. This allows for earlier diagnosis and treatment of thyroid disorders.</p> Signup and view all the answers

What is the biochemical definition of subclinical hyperthyroidism?

<p>Normal T4 &amp; T3 and suppressed TSH</p> Signup and view all the answers

What are the possible risks of subclinical hypothyroidism?

<p>Possible effects on foetal brain development in pregnancy, further progression to osteoporosis, atrial fibrillation, and thyrotoxicosis if exposed to iodine</p> Signup and view all the answers

What are the suggested groups to screen for subclinical thyroid disease?

<p>Women and those aged &gt;50 years</p> Signup and view all the answers

What are the levels of fT4 and TSH in example 1 of subclinical thyroid disease?

<p>fT4 : 28 pmol/L (10-23 pmol/L), TSH: &lt;0.01 mU/L (0.4-4 mU/L)</p> Signup and view all the answers

What are the indications for a radioactive iodine uptake test?

<p>Increased Thyroid hormone synthesis. Positive in Graves (homogeneous scan), multinodular goitre, toxic adenoma (heterogeneous scan). Often a follow-up test to establish the cause.</p> Signup and view all the answers

What does a positive TSH Receptor Antibodies test indicate?

<p>Graves disease. Useful if the radioactive iodine uptake test is not possible, contraindicated.</p> Signup and view all the answers

What is the significance of Thyroperoxidase antibodies?

<p>It signifies susceptibility to autoimmune thyroid disease and establishes the risk of thyroid disease in response to certain medications (e.g. amiodarone, lithium).</p> Signup and view all the answers

What is the role of Thyroglobulin in thyroid cancer?

<p>Thyroglobulin is used as a tumor marker to monitor for recurrence in cancer of the thyroid.</p> Signup and view all the answers

What are the clinical features of hyperthyroidism?

<p>Increased BMR, Tachycardia, Heat intolerance, Diarrhoea, Weight loss, Increased appetite, Moist, velvet skin, Anxiety</p> Signup and view all the answers

What are the clinical features of hypothyroidism?

<p>Decreased BMR, Bradycardia, Cold intolerance, Constipation, Weight gain, Decreased appetite, Dry coarse skin, Lethargy, Diminished fertility &amp; menstrual irregularities, Galactorrhoea, Delayed growth, Hyperlipidaemia, Muscle weakness</p> Signup and view all the answers

What are the primary causes of hyperthyroidism?

<p>Graves Disease, Toxic adenoma, Toxic multinodular goiter, Thyroiditis, T3 toxicosis</p> Signup and view all the answers

What are the primary causes of hypothyroidism?

<p>Hashimoto's Disease, Thyroiditis, Severe Iodine deficiency, Congenital defects, Iatrogenic, Hypopituitarism</p> Signup and view all the answers

What are the symptoms and characteristics of thyroid storm?

<p>Thyroid storm is a life-threatening condition characterized by acute severe exacerbation of symptoms, including coma, tachycardia, hyperpyrexia, marked anxiety/agitation, and risk of circulatory collapse. It is usually precipitated by major stress or illness such as surgery, trauma, or anesthesia. Thyroid hormone levels (T4/T3) are elevated, but not necessarily greater than usual.</p> Signup and view all the answers

What are the symptoms and characteristics of myxoedema coma?

<p>Myxoedema coma is a medical emergency characterized by hypothermia, depression of the respiratory center, reduced cardiac output leading to cerebral hypoxia. It may develop slowly, particularly in winter, or be precipitated by illness, exposure to cold, infection, or narcotics/analgesics.</p> Signup and view all the answers

What is the role of the laboratory in diagnosing and monitoring thyroid dysfunction?

<p>The laboratory plays a crucial role in confirming the diagnosis of thyroid diseases, as clinical symptoms alone may not be sufficient. Laboratory tests, such as measuring serum thyroid hormone levels (most often T4) and TSH, are the front line tests for diagnosis. The laboratory also monitors therapeutic efficacy in the treatment of thyroid dysfunction.</p> Signup and view all the answers

What are the possible causes of primary hyperthyroidism?

<p>Primary hyperthyroidism can be caused by conditions such as Graves' disease, toxic nodules, or pituitary disease. Additional tests for autoimmune diseases may be necessary to determine the underlying cause.</p> Signup and view all the answers

What are possible interferences in the Roche fT4 assay and what would the effects be on the result?

<p>High dose of biotin. Effect à Streptavidin antibodies. Effect à Anti-ruthenium antibodies à Blocking, or negatively interfering heterophilic antibodies à &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ ST ST ST ST T4-Biotin conjugate &gt;- Ru2+ -Ru2+ anti-T4 Buffered diluent ST -Streptavidin coated beads (magnetized) ST ST ST ST &gt;- Ru2+ -Sample T4 -Protein bound T4 &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ ST ST ST ST &gt;- Ru2+ &gt;- Ru2+ ST ST &gt;- Ru2+ ST ST ST ST ST &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ ST ST ST ST ST ST ST ST &gt;- Ru2+ &gt;- Ru2+ ST ST ST &gt;- Ru2+ &gt;- Ru2+ &gt;- Ru2+ ST ST ST ST ST ST ST ST Roche Elecsys –precautions…from Kit Insert Issues with T4 and T3 assays -past, present, and likely, future- Total vs Free Hormone Levels -measurement of total levels Previously up to late 1980s, reliable free hormone assays were not available. Traditional approach was to measure total T4 or T3; Interpretation of results required consideration of binding protein levels Drugs that increase TBG – Oestrogens, methadone, heroin, tranquilisers, clofibrate, 5-fluorouracil Drugs that decrease TBG – Glucocorticoids, androgens, anabolic steroids. Low TBG due to illness – Acute illness, nephrotic syndrome Inherited excess/deficient binding. – Familial dysalbuminaemic hyperthyroxinaemia – TBG variants (~40% of Indigenous Australians, lower affinity) Measurement of Total T4 assays-Influence of variant Thyroid Binding Globulin Total vs Free Hormone Levels -measurement of total levels Some drugs (e.g. salicylate) can displaces T4/T3 from their binding sites, influencing total levels, but not the biologically free levels* Results were therefore expressed as a free thyroi.</p> Signup and view all the answers

What is the traditional approach to measuring T4 or T3 levels and what was required for interpretation of the results?

<p>The traditional approach was to measure total T4 or T3 levels. Interpretation of the results required consideration of binding protein levels.</p> Signup and view all the answers

What are some drugs that increase TBG levels?

<p>Some drugs that increase TBG levels include oestrogens, methadone, heroin, tranquilisers, clofibrate, and 5-fluorouracil.</p> Signup and view all the answers

What are some drugs that decrease TBG levels?

<p>Some drugs that decrease TBG levels include glucocorticoids, androgens, and anabolic steroids.</p> Signup and view all the answers

More Quizzes Like This

Thyroid Hormones Functions and Disorders
10 questions
Thyroid Gland Function Quiz
29 questions
Hormone Regulation and Thyroid Function
8 questions
Use Quizgecko on...
Browser
Browser