Hypothyroidism

Question 1

define

Answer 1

underactive thyroid caused by low levels of T3 and T4

Question 2

two types of hypothyroidism

Answer 2

overt

subclinical

Question 3

causes of primary hypothyroidism

Answer 3

• goitrous e.g. Hashimoto’s thyroiditis, iodine deficiency, drug induced (amiodarone, lithium), maternally transmitted (ATDs) or hereditary biosynthetic defects
• non-goitrous e.g. atrophic thyroiditis, post-ablative therapy (RAI, surgery), post-radiotherapy (lymphoma treatment) or congenital development defect
• self-limiting e.g. withdrawal of ATDs, subacute thyroiditis with transient hypothyroidism and post-partum thyroiditis

Question 4

presentation

Answer 4

• hair and skin= coarse, sparse, dull, expressionless, periorbital puffy, pale, cool skin, vitiligo and hypercarotenaemia
• thermogenesis= cold intolerance
• fluid retention= pitting oedema
• cardiac= reduced HR, cardiac dilation, pericardial effusion and HF
• metabolic= reduced BMR, hyperlipidaemia, decreased appetite and weight gain
• GI= constipation, megacolon and ascites
• respiratory= deep hoarse voice, macroglossia and sleep apnoea
• CNS= depression, muscle cramps, peripheral neuropathy, lethargy, slow response, prolonged of tendon jerks, carpal tunnel, decreased visual acuity
• gynae/ reproductive= menorrhagia, olgio/amenorrhoea
• myxoedema
• babies can have cretinism (dwarfism and limited mental function)

Question 5

diagnosis of hypothyroidism

Answer 5

high TSH and low T3/4
high MCV, CK, LDL cholesterol and PRL
hyponatraemia (renal tubular water loss)
autoantibodies e.g. anti-TPO, anti-thyroglobulin and TSH receptor antibody

Question 6

management of hypothyroidism

Answer 6

levothyroxine

Question 7

dosing of levothyroxine

Answer 7

young= 50-100ug daily
elderly= 25-50ug daily
take before breakfast
adjust every 4 weeks according to respond
dose increased in pregnancy

Question 8

why is it important to begin levothyroxine slowly?

Answer 8

risk of cardiac arrhythmias

Question 9

how often should you check TSH when started on levothyroxine?

Answer 9

check TSH every 2 months after any dose change then once stabilised check every 12-18 months

Question 10

how to dose levothyroxine in secondary hypothyroidism?

Answer 10

titrate to T4 as TSH unreliable

Question 11

who does myxoedema coma usually affect?

Answer 11

typically elderly women with long standing but frequently unrecognised and untreated hypothyroidism

Question 12

diagnosis of myxoedema coma

Answer 12

• ECG= bradycardia, low voltage complexes, heart block T wave inversion and prolongation of QT interval
• type 2 respiratory failure= hypoxia, hypercarbia, respiratory acidosis
• co-existing adrenal failure

Question 13

management of myxoedema coma

Answer 13

• ABCDE, passively rewarm, aim for slow rise
• cardiac monitoring for arrhythmias and monitor urine output, fluid balance, central venous pressure, blood sugars and oxygenation
• broad spectrum antibiotics
• thyroxine cautiously and hydrocortisone if adrenal failure

Question 14

define Hashimoto’s thyroiditis

Answer 14

gradual failure of thyroid function, due to AI destruction, associated with other AI disease and HLA-DR3/5

Question 15

who does Hashimoto’s most commonly affect?

Answer 15

females 45-60

often FH

Question 16

presentation of Hashimoto’s

Answer 16

hashitoxicosis (transient hyperfunction)

risk of developing B cell NHL in affected gland

Question 17

diagnosis of Hashimoto’s

Answer 17

• antibodies e.g. anti-thyroglobulin and anti-thyroid peroxidae (TPO)