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NES Pharmacy CPD: Thyroid

NES Pharmacy CPD: Thyroid. Developed and delivered by Dr James Boyle. SpR in Endocrinology Glasgow Royal Infirmary February 2010 Amended by NES 2010. Glands and Hormones.

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NES Pharmacy CPD: Thyroid

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  1. NES Pharmacy CPD: Thyroid Developed and delivered by Dr James Boyle SpR in Endocrinology Glasgow Royal Infirmary February 2010 Amended by NES 2010

  2. Glands and Hormones • Endocrine Glands: Glands that secrete their products (hormones) directly into the bloodstream rather than through a duct • Hormone: Chemical substance formed in the body that is carried in the bloodstream to affect another part of the body.

  3. Thyroid gland • Secrets two iodinated hormones T3 and T4. • Responsible for optimal growth, development and function of body tissues. • The synthesis of T3 and T4 requires iodine. • Release of T3 and T4 controlled by negative feedback.

  4. TRH/TSH Feedback Loop

  5. TRH • Thyrotrophin releasing hormone. • Tripeptide produced by hypothalamus. • Release is pulsatile. • Downregulated by T3. • Travels through portal venous system to adenohypophysis. • Stimulates TSH synthesis and release.

  6. TSH • Thyroid stimulating hormone. • Produced by the pituitary gland • Upregulated by TRH • Downregulated by T4, T3 • Travels through portal venous system to cavernous sinus and body. • Stimulates several processes synthesis and release of hormones from the gland as well as gland growth

  7. Thyroid hormones (T4, T3) • T3/T4 enter circulation transported to plasma proteins (99%). • Thyroid only contributes 20% of the free circulating T3 with the rest produced by peripheral conversion of T4 to T3. T4 may be deiodinated to inactive reverse T3. • Regulation is based on the free component of thyroid hormone. • Action not understood but thought to involve high affinity binding sites in plasma membrane, mitochondria and nucleus resulting in protein synthesis and increased energy metabolism.

  8. Common diagnostic tools • TSH • Free T3, • Free T4 • Thyroid autoantiboides • Thyroid ultrasound • Radio-isotope uptake and scan • Fine need aspiration of thyroid

  9. Hypothyroidism • Clinical syndrome that results in deficiency of the thyroid hormones T4 and T3. • Common, prevalence 1-2% • F:M preponderance of 10:1 • Congenital hypothyroidism is 1:4000 live births in the UK.

  10. Types of hypothyroidism • Primary – Thyroid gland failure • Secondary – Pituitary failure • Tertiary – Hypothalamic failure • Sub-clinical

  11. Aetiology of hypothyroidism • Agenesis • Thyroid destruction • Hashimoto’s thyroiditis • Surgery • Radio-iodine ablation • Infiltration (tumour, sarcoidosis) • Inhibition of function • Iodine deficiency • Anti-thyroid medications (Carbimazole, PTU, lithium, amiodarone) • Inherited defects • Transient • Postpartum • Sub-acute thyroiditis • Secondary/Tertiary (pituitary, hypothalamic)

  12. Subclinical hypothyroidism • Estimated to affect 10% of females > 50yrs • Normal FT4/FT3, mildly elevated TSH • Few report symptoms • High risk of developing primary hypothyroidism • Can be associated with dyslipidaemia and subtle cardiac abnormalities. • Management a matter of clinical judgement

  13. Clinical Presentation • Symptoms – Tiredness, cold intolerance, weight gain, constipation, aches and pains, depression, psychosis, angina and menorrhagia. • Signs – Hair loss, hoarseness, goitre, bradycardia, dry skin, slow relaxing reflexes, anaemia, heart failure, effusions, carpal tunnel syndrome, mxyoedema coma.

  14. Diagnosis of hypothyroidism • Primary – Low FT4/FT3 and high TSH • Secondary – Low FT4/FT3 and low TSH • Tertiary – Low FT4/FT3 and low TSH • Sub-clinical – Normal FT4/FT3 and slightly high TSH

  15. Management • Apart from subacute and postpartum thyroiditis most require long term replacement in form of Levothyroxine. • Starting dose usually 50 -100mcg/daily. • Increased in steps of 25-50mcg every 4-6 weeks until FT4 is above middle of normal range and TSH normal/low normal. • Usual maintenance is 100mcg-200mcg/daily. • Suppressed TSH acceptable in certain cases

  16. Management • In cardiac disease cautious replacement is required to decompensation ie. Thyroxine 25mcg with steps of 25mcg only. • In secondary/tertiary cases ensure good adrenal reserve before commencing thyroxine replacement and dont use TSH to assess response. • In pregnancy requirements go up 50-100% and more monitoring is required. Use TSH to monitor at least every trimester.

  17. Management of subclinical cases • If TSH>10 – treat with thyroxine • If TSH 4-10 and asymptomatic – rpt TFT 6/12 • If TSH 4-10 and symptomatic or antibodies +ve or dyslipidaemia or history or radioiodine or surgery – treat with thyroxine

  18. Nurse Led Management • Patients often managed in nurse led clinics using questionnaire/algorithms. • Once patients with primary hypothyroidism are stable for 6 months (12 months for post radioiodine) they are discharged to GP for annual check. • Majority of patients unlikely to need to change dose of levothyroxine in the community.

  19. Hyperthyroidism • Clinical syndrome associated with raised levels of the thyroid hormones T4 and/or T3. • Can be increased production, release from damaged gland or exogenous T4. • Prevalence 1-2% • Incidence 3 per 1000 per year • Secondary hyperthyroidism due to increased TSH secretion is very rare (>1% of all cases) Common, prevalence 1-2%

  20. Aetiology of hyperthyroidism • Grave’s disease • Toxic multinodular goitre • Toxic adenoma • Thyroiditis (sub-acute, postpartum) • Drug induced (amiodarone) • Over treatment of T4 • TSH secreting adenoma

  21. Clinical Presentation • Symptoms – Heat intolerance, weight loss, loose motions, tremor, increased appetite, amenorrhoea, fatigue, anxiety, itch, angina. • Signs – Goitre, tachycardia, AF, tremor, warm hands, proximal myopathy, lid lag/retraction, Grave’s opthalmopathy, cardiac failure, hypertension, onycholysis, acropachy, pretibial myxoedema, thyroid storm .

  22. Diagnosis of thyrotoxicosis • Primary – High FT4 and/or FT3 and low TSH • Secondary – High FT4 and/or FT3 and high TSH • Sub-clinical – Normal FT4/FT3 and low TSH

  23. Grave’s disease versus Toxic MNG Grave’s Disease Multinodular Goitre Female>male Peak age >50 years Multinodular goitre Lid lag and retraction No skin, nail or finger changes Autoantibodies usually absent RAU patchy, irregular appearance • Female>male • Peak age 20-40 years • Diffuse and smooth • Lid lag and retraction, Grave’s eye signs, pretibial mxyoedma • Acropachy, onycholysis • Autoantibodies usually present • RAU scan uniform increased uptake

  24. Management • Carbimazole 20-40mg daily to render euthyroid (alternatively PTU). • Propanolol 40mg bd/tds to control symptoms in the short term. • Dose titration or “block and replace” regimen depending on individual practice. • Decision of definitive therapy needs to be made.

  25. Drugs • Carbimazole: Inhibits hormone production, side effects include rash and agranulocytosis (0.1%). • Propythiouracil: Inhibits hormone production as well as blocking T4 to T3 conversion, side effects include rash and agranulocytosis (0.4%).

  26. Pregnancy and lactation • Increased risk of fetal and neonatal thyrotoxicosis. • PTU preferred to Carbimazole due to less found in breast milk and less crossing placenta. • Carbimazole has been associated with aplasia cutis. • Requirements fall in Grave’s. • Lowest dose possible should be used. • Radio-iodine contra-indicated during pregnancy • TSH receptor titres should be determined early in third trimester to assess risk of neonatal thyroid dysfunction.

  27. Management • In Grave’s disease option to treat with drugs for 18 months and stop (50% chance of remission). Can also opt for radioiodine or surgery. • In toxic multinodular goitre/toxic adenoma need to use radioiodine or surgery to cure. Small number opt for long term drug therapy.

  28. Radio-iodine therapy • 131I is a safe and effective means of treatment. • Emits locally destructive beta particles to lead to cell damage and death over months. • Render euthyroid with drugs first and stop before to allow uptake of isotope. • In Glasgow, antithyroid drugs are not restarted afterwards unless thyrotoxicosis confirmed. • High risk of subsequent hypothyroidism.

  29. Nurse Led Management • Patients often managed in nurse led clinics using questionnaire/algorithms. • Very few if any patients discharged to GP on anti-thyroid drugs • Nurse led management appropriate if diagnosis made, decision of definitive therapy made and no complications. • Majority of patients unlikely to need to change dose of anti-thyroid drug in the long term.

  30. Pharmaceutical Care Issues – Hypothyroidism (examples) • Monitoring for signs & symptoms for dosage • Compliance can be a problem • Advise on treatment increments • Slow dose increments in heart disease • Anaemia can be associated with hypothyroid • Macrocytic mild anaemia (responds to thyroxine) • Pernicious anaemia common (treatment)

  31. Pharmaceutical Care Issues – Hyperthyroidism (examples) • Explain dosage regime for carbimazole • Monitor for side-effects of carbimazole • skin rashes, sore throat or mouth ulcers • Monitor for side-effects of beta blockers • Block & replace – also on thyroxine • Eye grittiness ->hypromellose eyedrops

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