Hypothyroidism

Question 1

what are the symptoms of primary hypothyroidism

Answer 1

tiredness
weight gain
puffy eyes and skin
feeling cold
slow heart rate
constipation
dry hair and skin
heavy periods
hyperlipidemia
TSH is elevated and T4 is decreased

Question 2

what are causes of primary hypothyroidism

Answer 2

Hashimoto’s thyroiditis
iatrogenic (post-surgery or radioactive iodine)
spontaneous atrophic
temporary thyroiditis (viral, post partum etc)
congenital
iodine deficiency
drug induced

Question 3

what is Hashimoto’s disease

Answer 3

antibodies attack thyroid and make it underactive
permanent
tendency can run in families

Question 4

how does iodine deficiency cause hypothyroidism

Answer 4

cannot manufacture enough thyroid hormone without iodine
TSH rises in response to fall in T4
high TSH stimulates hypertrophy of the thyroid gland

Question 5

thyroid hormone replacement

Answer 5

most patients are treated once daily with levothyroxine
half life is approximately 7 days
results in stable fT4 and fT3 levels
dose is commonly around 100mcg thyroxine
aim to normalise TSH
managed by GPs, no further investigations required if TSH is elevated

Question 6

management of hypothyroidism

Answer 6

monitoring of therapy - annual TFTs once stable, if dose changes wait at least 6 weeks before repeating TFTs
increased T4 requirement if starting oestrogen (OCP or HRT) or anticonvulsants

Question 7

what medications can impair T4 absorption

Answer 7

proton pump inhibitors (omeprazole, lansoprazole)
H2 antagonists (ranitidine)
iron, calcium, aluminium
don’t take T4 < 4hrs after these

Question 8

what is subclinical hypothyroidism

Answer 8

increased TSH but normal T4 and T3
TSH is more sensitive than T4
gradual occurrence (can be early sign of hypothyroidism)
main cause is autoimmune chronic thyroiditis
no convincing evidence it causes symptoms or has adverse effects

Question 9

management of subclinical hypothyroidism

Answer 9

treat is TSH >10 on 2 occasions and/or if TPOs are strongly positive

Question 10

what is secondary hypothyroidism

Answer 10

primary hypothyroidism should only be made if TSH is high
in pituitary disease TSH is low or (inappropriately) normal
in hypopituitarism, adequate replacement with thyroxine is judged by free T4 levels
low levels of TSH, T4 and T3 can also be caused by non-thyroidal illness