Hypothyroidism

Question 1

def

Answer 1

clinical syndrome from insufficient secretion of thyroid hormones

Question 2

aetiology

Answer 2

PRIMARY (decreased thyroid hormone production):
1 acquired
-autoimmune (hashimoto’s) thyroiditis (cellular & antibody-mediated)
-iatrogenic (post-surgery, medication for hyperthyroidism)
-severe iodine deficiency/iodine excess
-thyroiditis
2 congenital
-thyroid dysgenesis
-inherited defects in thyroid hormone synthesus

SECONDARY (<5% of cases):
-pituitary/hypothalamic disease (tumours) which result in decreased TSH/TRH & decreased stimulation of thyroid hormone production

Question 3

epi

Answer 3

more common in females

commonly >40yrs

Question 4

history

Answer 4

insidious onset
cold intolerance, lethargy, weight gain, constipation
mental slowness, depression
menstrual disturbances
history of surgery or radioiodine therapy for hyperthyroidism
personal or family history of other autoimmune conditions (addisons, T1DM)
myxoedema coma (severe hypothyroidism affecting brain functioning) which causes hypothermia, hypoventilation, hyponatraemia HF, confusion & coma

Question 5

examination

Answer 5

cold hands
head/neck/skin: pale puffy face, goitre, hair loss, dry skin
chest: bradycardia, pericardial/pleural effusions
abdomen: ascites

Question 6

investigations performed ins suspected hypothyroidism

Answer 6

1 bloods

• TFTs: primary shows decreased T3/T4 & increased TSH due to reduced negative feedback, secondary shows decreased T3/T4 & decreased or inappropriately normal TSH
• FBC: macrocytic anaemia
• UEs: may show hyponatraemia

2 pituitary function tests
3 pituitary MRI
4 visual field testing

Question 7

management

Answer 7

chronic

• levothyroxine (25-200micrograms/day
• rule out adrenal insufficiency before thyroid hormone replacement, treat adrenal insufficiency with hydrocortisone before giving levothyroxine to avoid an addisonian crisis
• patients with IHD, start on low dose and increase if ischaemic symptoms do not deteriorate

myxoedema coma

• oxygen
• warm patient
• rehydration
• IV T3/T4, IV hydrocortisone (incase hypothyroidism is secondary to hypopituitarism)
• treat underlying cause

Question 8

complications

Answer 8

myxoedema coma
myoxedema madness (psyhcosis with delusions & hallucinations) in severe hypothyroidism in elderly following levothyroxine

Question 9

prognosis

Answer 9

lifelong levothyroxine replacement therapy required

myxoedema coma mortality of 80%