Hypothyroidism

Question 1

Hpothyroidism definition

Answer 1

clinicla syndrome from insufficient secretion of thyroid hormones

Question 2

aetiology of primary hypothyroidism

Answer 2

low thyroid hormone production

acquired

• autoimmune thyroiditis - (Hashimotos) - cellular and Ab-mediated
• iatrogenic - post-surgery, radioiodine, medication for hyperthyroidism, amiodarone, lithium
• severe iodine deficiency or iodine excess - Wolff-Chaikoff effect
• thyroiditis - temporary hypo after hyper

congenital

• thyroid dysgenesis
• inherited defects in thyroid hormone biosynthesis

Question 3

secondary causes of hypothyroidism

Answer 3

pituitary/hypothalamic disease (eg tumour) = low TSH or TRH and low stimulation of thyroid hormone production

Question 4

epidemiology of hypothyroidism

Answer 4

female more

frequency from 0.1-2% of adults

>40yrs usually

iodine deficiency seen in mountainous areas eg Alps/Himalayas

Question 5

symptoms of hypothyroidism

Answer 5

onset usually insidious

cold intolerance

lethargy

weight gain

constipation

dry skin

hair loss

hoarse voice

mental slowness

depresion

dementia

cramps

ataxia

parasthesia

menstrual disturbances (irregular cycles, menorrhagia) in females

history of surgery or radioiodine therapy for hyperthyroidism

personal or FH of other autoimmune conditions eg Addisons, T1DM, pernicious anaemia, premature ovarian failure

myxoedema coma

Question 6

symptoms of myxoedema coma

Answer 6

(severe hypothyroidism usually seen in elderly)

hypothermia

hypoventilation

hyponatraemia

HF

confusion

coma

Question 7

signs of hypothyroidism

Answer 7

hands - bradycardia, cold hands

head/neck/skin - pale puffy face, goitre (lymphocytic and plasam cell infiltration), oedema, hair loss, dry skin, vitiligo

chest - pericardial/pleural effusions, CCF

abdo - ascites +- non-pitting oedema, ileus

neuro - slow relaxation of reflexes, signs of carpal tunnnel syndrome, ataxia, drowsy/coma

Question 8

investigations for hypothyroidism

Answer 8

Blood:

• TFT
  
  • Primary = high TSH, low T3/4
  • secondary = low TSH/normal = low T3/4
  • subclinical - high TSH and normal T3/4
• FBC - normocytic anaemia
• UE - low Na
• cholesterol might be high

in suspected secondary cases - pit func tests, pit MRI and visual field testing

Question 9

Management of chronic hypothyroidism

Answer 9

levothyroxine 25-200ug/day

rule out underlying adrenal insufficiency and treat before thyroid hormone replacement to avoid Addisonian crisis

Adjust dosage depending on TFT and clinical pic - 6wk

if IHD - start 25ug/day and increase in 6wk intervals if ischemic symptoms dont get worse

Question 10

treatment of myxoedema coma

Answer 10

oxygen

rewarming

rehydration

IV T4/T3

IV hydrocortisone - incase hypothyroidism is secondary to hypopit

treat underlying disorder eg infection

Question 11

complications of hypothyroidism

Answer 11

myxoedema coma

myxoedema madness - psychosis with delusions and hallucinations or dementia - seen in elderly after starting levothyroxine

Question 12

prognosis of hypothyroidism

Answer 12

lifelong levothyroxine is needed

myxoedema coma has mortality of up to 80%

Question 13

RF of hypothyroidism

Answer 13

other autoimmune disease - T!DM, Addisons and PA

Turner’s and Down’s syndromes, cystic fibrosis, primary biliary cholangitis, ovarian hyperstimulation

POEMS syndrome—polyneuropathy, organomegaly, endocrinopathy, m-protein band (plasmacytoma) + skin pigmentation/tethering.

genetic - dyshormonogenesis eg Pendred’s syndrome with deafness, increased uptake on isotope scan, displaced by K perchlorate

Question 14

pregnancy problems with hypothyroidism

Answer 14

eclampsia

anaemia

prematurity

low birthweight

stillbirth

PPH