Thyroid function tests

Thyroid function tests An endocrine registrar opinion  Our Normal Range    FT4 pmol/L 11.5 – 23 FT3 pmol/L 3-6.7 TSH 0.3-5.5 mu/L  An exhaustive (? And exhausting) trawl through TFTs – please tell me if I have missed any that have worried you. Requested by GP  Male age 40 years –palpitations and mild proptosis – smallish smooth goitre   FT4 80 TSH <0.01 Graves’ disease  Block and replace   Carbimazole 40mg od or PTU 200mg bd Add in thyroxine 75 to 100g after 6 weeks  Treat for 6 mths  Relapse – treat radioiodine ? With steroid cover or total thyroidectomy  ? Titration carbimazole ? Radioiodine at referral Requested by GP  Female age 76yrs – gradual weight loss solitary thyroid nodule   FT4 32 TSH <0.01 Management toxic nodule   Radioactive iodine ? FNA first if palpable nodule as low risk of malignancy in toxic nodules Requested endocrine SHO  Female 4 weeks post radioiodine   fT4 11 TSH 0.02 Post radioiodine thyroid function    Depends on dose if aim ablation then recheck in 2-4 weeks and if TSH > 6 start thyroxine (exemption form) If low moderate dose – recheck 4-6 weeks but do not treat until frankly hypothyroid TFTs may fluctuate post radioiodine with antibody titre   apparent recovery of function hypothyroid for >1 year stable for discharge Requested by the Medical HP  Female age 79yrs with fast AF   FT4 21 TSH 0.2 Normal FT4 with a suppressed but detectable TSH  Probably not for antithyroid treatment  Thyroid scintigram may show area of uptake with relative suppression of the rest of the gland – evolving autonomous function  Any patient with abnormal TFTs and AF ask re amiodarone Requested by the medical registrar  VT with poor LV function controlled on amiodarone    FT4 50 FT3 7 TSH <0.01 Amiodarone and the thyroid     Inhibits thyroidal iodide uptake Inhibits conversion T4 to T3 intracellularly Inhibits T4 entry into cells Direct T3 antagonism at level of cardiac tissue What does it do to TFTs   Early – 1st 10 days  TSH  FT3  Reverse T3  then FT4  after 4th day FT4  by 40% (not necessarily thyrotoxic) FT3 remains low or normal TSH levels normalise as FT4 levels rise to overcome the partial block in T3 production TSH may suppress partial T3 agonist effect Later - 1-4mths     Longterm  Amiodarone induced hyperthyroidism 2-12%  Type 1 –   Iodine overload in abnormal gland treat with high dose carbimazole +/- potasium perchlorate or lithium Glandular damage - release of preformed hormones treat with prednisolone 0.5-1.25mg/kg for 3-6wks  Type 2 –    Management of the tachyarrythmia    blockers not if CCF ?total thyroidectomy (not radioiodine) GP referral to endocrine clinic  Recent flu – tender enlargement thyroid   T4 28 TSH <0.01 De Quervains thyroiditis      Recheck TFTs  probably hypothyroid by then Thyroid antibodies and ESR Thyroid scintigram – reduced uptake Symptomatic treatment with NSAIDs Warn re the possibility of recurrence Requested by ITU sister  Female age 25years – hyperpyrexia, profound muscle weakness requiring ventilation   FT4 210 TSH <0.01 Thyrotoxic crisis    Carbimazole 60 –100mg via ng tube Propranolol infusion Profound myopathy and even neuropathy can be associated with Graves’ NB myasthenia Requested Ophthalmology registrar  History last year of weight loss and sweats spontaneously resolved now unilateral marked proptosis with papilloedema and colour blindness    FT4 10 TSH 6.5 Microsomal and thyroglobulin antibodies markedly positive Management     Thyroxine Hypermellose eye drops Steroids – 60mg Bone protection Requested by cardiac SHO  Pre coronary artery bipass surgery   FT4 4 TSH 40 Management hypothyroidism with coronary artery disease   May need to put in stents to allow introduction of triodothyronine and then thyroxine NB some patients symptomatic (pressure on chest/palpitations) when thyroxine started/increased – NO evidence of CAD or SVT Requested by the GP  Female age 32 years – weight gain and tired   TSH 5.5 FT4 13 Management borderline hypothyroidism   “Your weight gain and tiredness is not related to the thyroid – thyroxine increases metabolic rate and may give you a temporary boost but your symptoms will return when the axis readjusts itself” Other endocrine conditions - weight energy    Cushing’s which is usually easily excluded without investigations Growth hormone deficiency Hypothalamic eating disorders Requested by endocrine registrar  Hypothyroid on replacement Thyroxine 400g   FT4 23 TSH 15 Hypothyroidism requiring high dose/variable dose replacement    Check the tablets each visit – check compliance with the GP (but likely over and underdosing at times) Check for malabsorption but unlikely the cause Probably continue to see but at infrequent intervals Requested by GP  Female age 38years – oligoammenorrhoea and tiredness – family history of thyroid disease    FT4 12 TSH 6.5 FSH 20 Management polyendocrine disease    Repeat FSH – day 1-5 in the cycle – perimenapause the FSH can vary with each cycle – remember resistant ovary syndrome Check autoantibody screen (? Ovarian antibodies) – if high titre thyroid antibodies treat if TSH  8 mu/L or FT4 < 11pmol/L Synacthen probably unnecesary Requested by the casualty officer  Female age 60 years – found collapsed at home – history of epilepsy   FT4 10.5 TSH 0.23 Low T4 normal TSH     Sick euthyroid ? Treat probably not Possibly hypopituitary – cortisol/FSH/LH Check medication – can be secondary to carbamazepine Can be normal for the patient – check old TFTs Requested by GP  Female age 38years secondary ammenorrhoea   FT4 9 TSH 1.2 Hypopituitarism     FSH/LH/prolactin/cortisol low normal MRI pituitary partially empty fossa or large chromophobe adenoma Start hydrocortisone ?10 and 5mg whilst organising 9am cortisol and ? glucagon test Start thyroxine replacent a week later Requested diabetes specialist nurse  Type 1 diabetes and 18 weeks pregnant with severe hypos   FT4 11.0 TSH 0.8 Low T4 in pregnancy    Should we treat lowest 25th centile FT4 and and highest 25th centile TSH with thyroxine ?100g If so ? screen high risk women who attend for prepregnancy counselling e.g. diabetics Lymphocytic hypophysitis -  insulin requirements more likely previous poor compliance! Requested by the obstetric SHO  Admitted with hyperemesis gravidarum – pulse 110bpm   FT4 29 TSH <0.01 Management   Usually HCG induced in which case will resolve spontaneously by around 14 weeks If positive thyroid antibodies or history of Graves’ disease then can treat with PTU or carbimazole < 30mg Requested by paediatric SHO  New born baby – Mum Hashimoto’s   FT4 18 TSH 20 Management   TSH – physiological surge after birth finished by 72 hours Guthrie test performed at 10 days post delivery   TSH of 10 taken as cut off for a positive No lower limit  Cretinism related to maternal blocking antibodies or failure of thyroid development (Di George syndrome) Obstetric registrar    Mum hypothyroid on replacement – 28wks pregnant – scan shows fetal tachycardia and heart failure FT4 16 TSH 1.0 Fetal thyrotoxicosis   Mum previous Graves’ treated with radioiodine TSH receptor antibody mediated - measure   Graves’ radioiodine ablated or thyroidectomy ?NOT IF Graves’on treatment - thyroid status /dose requirement will indicate antibody level  Treat block and replace (ONLY indication in pregnancy – otherwise thyrotoxicosis – titration dose PTU or carbimazole) Requested by GP  Tired 10 weeks post partum   FT4 32 TSH 0.2 or 9 or 8 Post partum thyroiditis     Scintigram diagnostic but not necessary Thyroid antibodies may be positive  autoimmune condition cf De Quervains which is viral Toxic phase  ?symptomatically with propranolol thyroxine around 50% will be permanent continue through next pregnancy if within a year Hypothyroid phase   Requested by the surgical registrar  Female age 30years new thyroid enlargement ?? Cancer    FT4 12 TSH 6 Thyroid microsomal and thyroglobulin antibodies strongly positive New thyroid swelling   Hashimotos disease  Scintigram will show poor uptake, US nodular gland   If obvious palpable mass within thyroid then FNA A bleed into a follicle can present with overnight appearance of mass – FNA will reveal blood stained fluid Thyroxine Requested by Consultant Endocrine surgeon  Long standing goitre   FT4 28 TSH 7 Measureable TSH with raised FT4   Heterophile antibodies – usually not above 1 TSH resistance syndromes   Central (clinically toxic) Peripheral (clinically euthyroid) very rare but almost always had antithyroid treatment +/- thyroidectomy by the time of diagnosis  TSH oma  Requested by the endocrine SpR  Follicular Cancer of the thyroid on thyroxine replacement     FT4 24 FT3 6.2 TSH 0.9 Thyroglobulin 9 Follow up of thyroid cancer  Original diagnosis and treatment   <2cm papillary may be lobectomy only in which case thyrogobulin will be detectable > 2cm should have had total thyroidectomy and ablative radioiodine - thyroglobulins usually undetectable if TSH unrecordable  If suspect relapse – I131 scan with TSH > 18 (stop thyroxine and convert to T3 6 weeks before – stop both 2 weeks before or give TSH)