GUIDELINES FOR THYROID
                                                         FUNCTION TESTING
                         ...
GUIDELINES FOR THYROID
                                                       FUNCTION TESTING
                           ...
GUIDELINES FOR THYROID
                                                          FUNCTION TESTING
                        ...
GUIDELINES FOR THYROID
                                                           FUNCTION TESTING
                       ...
GUIDELINES FOR THYROID
                                                            FUNCTION TESTING
                      ...
GUIDELINES FOR THYROID
                                                           FUNCTION TESTING
                       ...
GUIDELINES FOR THYROID
                                                          FUNCTION TESTING
                        ...
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GUIDELINES

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Transcript of "GUIDELINES"

  1. 1. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 GUIDELINES FOR THYROID FUNCTION TESTING EDITION No 1 DATE OF FIRST ISSUE Sep 2009 REVIEW INTERVAL 2 Yearly AUTHORISED BY Medical Director AUTHOR Dr Ken Graham COPY 1 LOCATION OF COPIES 1. Medical Director 2. Laboratory guidelines3288.doc Page 1 of 7 Version 1 Aug 2009 Authorised by Medical Director
  2. 2. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 CONTENTS 1.0 INTRODUCTION Page 3 1.1 THYROID DISORDERS 1.2 THYROID FUNCTION TESTS 1.3 NEED FOR GUIDELINES 2.0 INDICATIONS FOR THYROID FUNCTION TESTING Page 4-5 2.1 INTRODUCTION 2.2 SCREENING FOR THYROID DYSFUNCTION 2.2.1 GOITRE AND NODULES 2.2.2 ATRIAL FIBRILLATION OSTEOPOROSIS SUBFERTILITY 2.2.3 WOMEN WITH TYPE 1 DIABETES MELLITUS 2.2.4 THE NORMAL HEALTHY ADULT POPULATION 2.2.5 HOSPITAL IN PATIENTS 3.0 SURVEILLANCE OF THYROID FUNCTION Page 6 3.1 HISTORY OF POST-PARTUM THYROIDITIS 3.2 PATIENTS WITH DIABETES MELLITUS 3.3 PATIENTS WITH SOME CHROMOSOMAL ABNORMALITIES 3.4 PATIENTS ON AMIODARONE OR LITHIUM 3.5 FOLLOWING I131 OR THYROID SURGERY 4.0 MONITORING OF THYROID FUNCTION Page 7 4.1 TREATMENT OF THYROTOXICOSIS WITH ANTITHYROID DRUGS 4.2 PATIENTS ON THYROXINE guidelines3288.doc Page 2 of 7 Version 1 Aug 2009 Authorised by Medical Director
  3. 3. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 1.0 INTRODUCTION 1.1 THYROID DISORDERS Thyroid disorders are one of the most prevalent medical conditions seen. Disorders include hypothyroidism, sub-clinical hypothyroidism, hyperthyroidism, goitre and thyroid cancer. Hypothyroidism often presents insidiously, the prevalence is about 2%; it is more common in older women and ten times commoner in women than men. Hyperthyroidism is often more obvious than hypothyroidism and causes significant Morbidity. The usual cause is autoimmune (Graves’ disease) it is about as prevalent as hypothyroidism, and again ten times more common in women that men. 1.2 THYROID FUNCTION TESTS Thyroid function testing is common with approximately 10 million requests each year in the UK costing an estimated £30 million. Shetland has similar figures with an estimated yearly spend on reagents of £17,000 in 2008-2009. 1.3 NEED FOR GUIDELINES Many Doctors are uncertain about many aspects of thyroid function testing. Guidelines do exist. This document is a summary of the UK National Guideline. guidelines3288.doc Page 3 of 7 Version 1 Aug 2009 Authorised by Medical Director
  4. 4. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 2.0 INDICATIONS FOR THYROID FUNCTION TESTING 2.1 INTRODUCTION Hypothyroidism is an insidious condition with significant morbidity. The earliest biochemical abnormality in hypothyroidism is an increase in serum Thyroid Stimulating Hormone (TSH) associated with normal free thyroxine (FT4) and free tri-iodothyronine (FT3) concentrations, this is known as sub-clinical hypothyroidism. Often there is a steady decline in FT4 concentrations, at which stage most patients will have symptoms and benefit from thyroxine replacement. Sub-clinical hypothyroidism is particularly common in elderly women with approximately 10% of women over the age of 60 having TSH levels above the reference range. Hyperthyroidism has significant short-term morbidity and is often easier to pick up clinically. Sub-clinical hyperthyroidism is defined as a low TSH concentration and normal FT4 and FT3 concentrations. This pattern should be interpreted with caution since it may reflect hypothalamic disorder, pituitary disease, non- thyroid illness or taking medications that inhibit TSH secretion. 2.2 SCREENING FOR THYROID DYSFUNCTION 2.2.1 GOITRE AND NODULES All patients with a suspected goitre should have a TSH estimation to detect unapparent hypo or hyperthyroidism. 2.2.2 ATRIAL FIBRILLATION OSTEOPOROSIS SUBFERTILITY Thyrotoxicosis is a recognised cause of atrial fibrillation; approximately 10% of patients with thyrotoxicosis have atrial fibrillation. Hyperthyroidism is a potential reversible cause of osteoporosis. Both hypo and hyperthyroidism can be associated with abnormal menstrual cycles, foetal loss and sub fertility. It is recommended that these patients have TSH checked at presentation. guidelines3288.doc Page 4 of 7 Version 1 Aug 2009 Authorised by Medical Director
  5. 5. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 2.2.3 WOMEN WITH TYPE 1 DIABETES MELLITUS These patients are three times more likely to develop post partum thyroid dysfunction. They should have TSH and FT4 and thyroid peroxidase antibodies (TPOAb) checked when pregnant at first booking and at 3 months post partum. 2.2.4 THE NORMAL HEALTHY ADULT POPULATION Screening for thyroid dysfunction in a healthy adult population is not warranted. If screening is performed, and a high TSH concentration is found, and FT4 is normal the measurement should be repeated at 6 months, after excluding non-thyroid illness and drug interference. If the TSH is >10mU/L and the FT4 is low then the patient has overt hypothyroidism and should be treated with thyroxine. If the FT4 is normal but the TSH is >10mU/L then treatment with thyroxine is recommended. If the TSH is above the lab reference range (currently 03.5mU/L) but <10mU/L then TPOAb should be checked. If these are elevated then check TSH annually. Start thyroxine if TSH>10mU/L or if symptomatic refer to thyroid clinic at Gilbert Bain Hospital. If the antibody concentration is not raised then repeat TSH every three years. There is no evidence to support the use of thyroxine in non-pregnant patients with a TSH above the reference range but <10mU/L 2.2.5 HOSPITAL IN PATIENTS Isolated alterations in TSH concentration (low and high) occur in approximately 15% of patients due to altered TSH secretion in response to drugs or non-thyroid illness. Routine testing of in patients admitted acutely to hospital is not warranted unless specific clinical indications exist. guidelines3288.doc Page 5 of 7 Version 1 Aug 2009 Authorised by Medical Director
  6. 6. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 3.0 SURVEILLANCE OF THYROID FUNCTION 3.1 HISTORY OF POST PARTUM THYROIDITIS These patients will have an increased risk of permanent hypothyroidism. Check TSH yearly and FT4 and TSH 8 weeks after future pregnancy. 3.2 PATIENTS WITH DIABETES MELLITUS Patients with type 1 diabetes should have thyroid function checked yearly. Patients with type 2 should have thyroid function checked at diagnosis, routine annual testing is not then required. 3.3 PATIENTS WITH SOME CHROMOSOMAL ABNORMALITIES There is a high incidence of hypothyroidism in Down Syndrome and Turner's Syndrome, check TSH yearly. 3.4 PATIENTS ON AMIODARONE AND LITHIUM Amiodarone contains 75mg of Iodine per 200mg tablet and is frequently associated with thyroid abnormalities. Lithium treatment is associated with mild hypothyroidism. Check FT4 and TSH prior to starting Amiodarone, monitor every six months. Amiodarone has a very long half-life monitor for a further year after stopping Amiodarone. Patients on Lithium need FT4 and TSH tested prior to starting and every six months until drug is discontinued. 3.5 FOLLOWING I131 OR THYROID SURGERY Indefinite surveillance looking for hypothyroidism. Check TSH and FT4 8 weeks post treatment, then 3 monthly for one year, then yearly. guidelines3288.doc Page 6 of 7 Version 1 Aug 2009 Authorised by Medical Director
  7. 7. GUIDELINES FOR THYROID FUNCTION TESTING Version 1 Sep 2009 4.0MONITORING OF THYROID FUNCTION 4.1 TREATMENT OF THYROTOXICOSIS WITH ANTITHYROID DRUGS Check TSH and FT4 every 3 months when initiating treatment until stable. Check annually if used long term. 4.2 PATIENTS ON THYROXINE Once hypothyroidism has been diagnosed and the dose is established this stays constant in most patients. Once treatment is initiated then long term follow up with annual measurements of TSH is required to check concordance. In pregnancy doses may need to be increased. 5.0 guidelines3288.doc Page 7 of 7 Version 1 Aug 2009 Authorised by Medical Director

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