Thyroid disorders

Question 1

What does free T4 reflect about thyroid health?

Answer 1

Most direct reflection of thyroid function

inc during febrile illness

May be altered in preg

Question 2

What does serum TSH reflect about thyroid health?

Answer 2

Most sensitive for hypothyroid state

Elevated before dec in T4 detected

No very reliable for hyperthyroidism

Question 3

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

Answer 3

Hypothyroidism

Question 4

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

Answer 4

Hyperthyroidism

Question 5

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

Answer 5

Mild/early or subclinical hypothyroidism

Question 6

What are the sx of hypothyroidism?

Answer 6

Unexplained weight gain, puffiness

Cold intolerance

bradycardia

constipation

somnolence, lethargy, fatigue, forgetfulness

reduce reflexes

menorrhagia

course hair, dry flaky skin

Question 7

What are the sx of hyperthyroidism?

Answer 7

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

Question 8

What conditions commonly cause hyperthyroidism?

Answer 8

Thyroid adenoma

Subacute thyroiditis

Grave’s disease

Toxic nodular goitre

Question 9

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

Answer 9

Goals = dec thyroid overproduction, block effects of excess T4

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

Question 10

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

Answer 10

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

Question 11

What is the clinical presentation of Grave’s Disease?

Answer 11

Hyperthyroidism

Diffuse thyroid enlargement

Exopthalmos (eyeball protrusion), stare and lid lag

Periorbital oedema

Question 12

What is the pathophysiology of toxic nodular goitre?

Answer 12

Underlying cause unknown

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

Question 13

What is the clinical presentation of toxic nodular goitre?

Answer 13

Hyperthyroidism

One or more nodular masses (not an obvious goitre)

Dont tend to have ophthalmopathy

Cardiac abnormalities common = CHF, tachyarrhythmias

Question 14

What is a thyroid storm?

Answer 14

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

May lead to HF or coma

Question 15

What are the sx of a thyroid storm?

Answer 15

Marked weight loss

Rising fever

Tachycardia

CNS dysfunction

GI sx

Restlessness, tremor

Question 16

How is thyroid storm treated?

Answer 16

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

Question 17

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

Answer 17

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

Carbimazole = prevents the synthesis of new

Question 18

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

Answer 18

Lugol solution

Dexamethasone

Question 19

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

Answer 19

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

Esmolol

Metoprolol

Question 20

What are the 4 ways to treat hyperthyroidism?

Answer 20

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

Question 21

What are the indications for PTU and carbimazole?

Answer 21

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

Question 22

What are the serious ADRs of PTU and carbimazole?

Answer 22

Agranulocytosis = susceptible to infection

Thrombocytopenia

drug fever

hepatitis

Question 23

How is lugol solution used in acute thyrotoxicosis?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

What is hypothyroidism?

Answer 25

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

Question 26

What is the difference between primary and secondary hypothyroidism?

Answer 26

Primary = thyroid cant produce amount of hormone pituitary calls for
- usually permanent

Secondary = thyroid isnt being stimulated by pituitary to produce hormone

Question 27

What can cause primary hypothyroidism?

Answer 27

Disease = hashimotos

Medical therapies = radiation, surgical, antithyroid drugs

Dietary iodine def

Drug induced (amiodarone, lithium)

Failure of gland to develop of congenital incompetence

Question 28

What is the MOA of Hashimoto’s diseas?

Answer 28

Chronic autoimmune disease

Immune reaction against thyroglobulin or some other component of thyroid tissue –> can lead to myxoedema or hypothyroidism

Question 29

What are the early clinical features of hypothyroidism?

Answer 29

Lethargy

Fatigue

forgetfulness

cold intolerance

unexplained weight gain

constipation

Question 30

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

Answer 30

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

Question 31

What are the sx of myxoedema?

Answer 31

Hypothermia, hypoglycaemia, weakness, stupor, shock

Question 32

How is hypothyroidism treated?

Answer 32

Replacement therapy w/ a thyroid hormone preparation

Modify Tx if = ischaemic heart disease, preg

Question 33

How is T4 useful in hypothyroidism?

Answer 33

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

Question 34

What are the ADRs of thyroxine?

Answer 34

Lacks T3-induced DRs (tremor, headache, palpitations, diarrhoea)

If hyperthyroidism occurs, stop thyroxine for a week and then re-introduce at lower dose

Question 35

How is T3 useful in hypothyroidism?

Answer 35

More rapid onset, shorter duration

More potent

Initiation treatment in severe hypothyroidism

Used in those w/ documented intolerance or resistance to thyroxine sodium

Question 36

What types of thyroid disorders are common in pregnant women?

Answer 36

Subclinical hypothyroidism - 2-3%

Postpartum thyroiditis - 4-10%

Question 37

What are the phases of post-partum thyroiditis?

Answer 37

Hyperthyroid phase - damage to thyroid –> release of stored hormone

hypothyroid phase

Resolution phase (euthyroid) phase

Women w/ autoimmune disease = higher incidence of PPT

Question 38

How is pre-existing hyperthyroidism tx in pregnancy?

Answer 38

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

Question 39

How is hypothyroidism tx in pregnancy?

Answer 39

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