Thyroid disorders Flashcards by Anika Gouws

What does free T4 reflect about thyroid health?

Most direct reflection of thyroid function

inc during febrile illness

May be altered in preg

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What does serum TSH reflect about thyroid health?

Most sensitive for hypothyroid state

Elevated before dec in T4 detected

No very reliable for hyperthyroidism

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In what condition will you have low T4 and high TSH?

Hypothyroidism

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In what condition will you have high T4 and low TSH?

Hyperthyroidism

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In what condition will you have normal T4 and high TSH?

Mild/early or subclinical hypothyroidism

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What are the sx of hypothyroidism?

Unexplained weight gain, puffiness

Cold intolerance

bradycardia

constipation

somnolence, lethargy, fatigue, forgetfulness

reduce reflexes

menorrhagia

course hair, dry flaky skin

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What are the sx of hyperthyroidism?

Weight loss despite inc appetite

heat intolerance

palpitations, tachycardia

diarrhoea

fatigue wakefulness, nervousness, emotional lability

Proximal muscle weakness, tremor

irregular menstruation

thick hair, moist skin

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What conditions commonly cause hyperthyroidism?

Thyroid adenoma

Subacute thyroiditis

Grave’s disease

Toxic nodular goitre

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Generally, what are the treatments and treatment goals of hyperthyroidism?

Goals = dec thyroid overproduction, block effects of excess T4

Tx = antithyroid drugs, radioactive iodine (RAI), surgery

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What is the pathophysiology of Grave’s disease (diffuse toxic goitre)?

Usually in young women

Formation of antibodies directed against the TSH-R on the surface of thyroid cells –> antibodies stimulate receptor in same manner as TSH –> overproduction/release of thyroid hormone

Antibodies = LATS –> long-acting thyroid stimulators

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What is the clinical presentation of Grave’s Disease?

Hyperthyroidism

Diffuse thyroid enlargement

Exopthalmos (eyeball protrusion), stare and lid lag

Periorbital oedema

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What is the pathophysiology of toxic nodular goitre?

Underlying cause unknown

thyrotoxicosis = one or more nodules autonomously secreting excessive thyroid hormone (suppresses the rest of the gland)

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What is the clinical presentation of toxic nodular goitre?

Hyperthyroidism

One or more nodular masses (not an obvious goitre)

Dont tend to have ophthalmopathy

Cardiac abnormalities common = CHF, tachyarrhythmias

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What is a thyroid storm?

Medical emergency w/ exaggerated sx of hyperthyroidism precipitated by severe stress, trauma, or infection

May lead to HF or coma

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What are the sx of a thyroid storm?

Marked weight loss

Rising fever

Tachycardia

CNS dysfunction

GI sx

Restlessness, tremor

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How is thyroid storm treated?

IV fluids, high dose antithyroid drugs (PTU preferred, propranolol and corticosteroids

Iodine, lithium, paracetamol and rehydration may also be used

Amiodarone should be avoided in A-fib due to severe hyperthyroidism as iodine content impairs anti-thyroid drugs

What drugs stop the synthesis of thyroid hormone in a thyroid storm?

Propylthiouracil (PTU) - is able to prevent conversion of already secreted T4 into T3

Carbimazole = prevents the synthesis of new

What drugs prevent the release of thyroid hormone from the gland in a thyroid storm?

Lugol solution

Dexamethasone

What drugs can be used to treated the tachycardia associated with a thyroid storm?

Propranolol = good because it is non-selective and will get beta 1-2 and alpha 1

Esmolol

Metoprolol

What are the 4 ways to treat hyperthyroidism?

1) kill thyroid using PTU and carbimazole –> then supplemental thyroid hormone

2) Cut out thyroid, using PTU/carbim beforehand –> then supplement with thyroid hormone

3) Long term PTU and carbim –> body stops producing thyroid hormone

4) Titrate carbimazole dose to dec response of the thyroid

What are the indications for PTU and carbimazole?

Thyroid storm

Grave’s disease - if remission achieved given for 12-18 months

Adjunctive therapy with radioactive iodine until radiation takes effect

Pre-operative preparation to establish and maintain euthyroid state until surgery can be performed

What are the serious ADRs of PTU and carbimazole?

Agranulocytosis = susceptible to infection

Thrombocytopenia

drug fever

hepatitis

How is lugol solution used in acute thyrotoxicosis?

Used short term

Acts immediately to inhibit release of thyroid hormone

Plasma levels decline as circulating hormones are degraded

Sx improve w/in 2-7 days, effect limited to several weeks because thyroid escapes drugs inhibitory effects

When/how is radioactive iodine (RAI) used in hyperthyroidism?

MOA = selectively taken up by thryoid gland –> destroys cells that would otherwise concentrate iodine and produce T4 –> dec thyroid hormone production

Indication = Grave’s disease, nodular goitre

What is hypothyroidism?

Decreased activity of thyroid gland = slows rate of metabolism causing mental and physical sluggishness

What is the difference between primary and secondary hypothyroidism?

Primary = thyroid cant produce amount of hormone pituitary calls for - usually permanent Secondary = thyroid isnt being stimulated by pituitary to produce hormone

What can cause primary hypothyroidism?

Disease = hashimotos Medical therapies = radiation, surgical, antithyroid drugs Dietary iodine def Drug induced (amiodarone, lithium) Failure of gland to develop of congenital incompetence

What is the MOA of Hashimoto's diseas?

Chronic autoimmune disease Immune reaction against thyroglobulin or some other component of thyroid tissue --> can lead to myxoedema or hypothyroidism

What are the early clinical features of hypothyroidism?

Lethargy Fatigue forgetfulness cold intolerance unexplained weight gain constipation

What are the signs and sx of progressed hypothyroidism/myxoedema?

Dry, flaky, inelastic skin Coarse hair slowed speech and thought hoarseness Slow return of deep tendon reflexes (esp in achillies) Puffy face, hands, feet eyelid droops hearing loss menorrhagia dec libido

What are the sx of myxoedema?

Hypothermia, hypoglycaemia, weakness, stupor, shock

How is hypothyroidism treated?

Replacement therapy w/ a thyroid hormone preparation Modify Tx if = ischaemic heart disease, preg

How is T4 useful in hypothyroidism?

Used in primary and secondary hypothyroidism due to long half-life, once daily orally <60 y/o w/out ischaemic HD = 50-100mcg, inc over 3-6 months Elderly = 25 - 50 mcg, inc over 3-6 months to 100-150mcg

What are the ADRs of thyroxine?

Lacks T3-induced DRs (tremor, headache, palpitations, diarrhoea) If hyperthyroidism occurs, stop thyroxine for a week and then re-introduce at lower dose

How is T3 useful in hypothyroidism?

More rapid onset, shorter duration More potent Initiation treatment in severe hypothyroidism Used in those w/ documented intolerance or resistance to thyroxine sodium

What types of thyroid disorders are common in pregnant women?

Subclinical hypothyroidism - 2-3% Postpartum thyroiditis - 4-10%

What are the phases of post-partum thyroiditis?

Hyperthyroid phase - damage to thyroid --> release of stored hormone hypothyroid phase Resolution phase (euthyroid) phase Women w/ autoimmune disease = higher incidence of PPT

How is pre-existing hyperthyroidism tx in pregnancy?

PTU (tri 2-3)/ carbimazole (tri1) using smallest possible dose Transplacental passage of anti-thyroid drugs = foetal goitre If uncontrolled: - BB - short period okay - iodine - short period okay - NOT RAI

How is hypothyroidism tx in pregnancy?

Goal = normalise maternal TSH Ideally --> correct before conception TSH and thyroxine lvls used to optimise therapy Thyroxine replacement needs to be inc by 30-50% at about 4-6 wks gestation