hypothyroidism W6 Flashcards
TFT (thyroid function tests) in primary hypothyroidism?
increased TSH, decreased FT4 (free T4)
primary hypothyroidism and gender?
more common in women
symptoms of hypothyroidism
tired
weight gain, puffy eyes and skin
feeling cold
slow heart rate
constipation
dry hair and skin
heavy periods
hyperlipidaemia
enlarged thyroid (goitre)
T4 name?
thyroxine
when shouldn’t patients be treated with thyroxin even if they have symptoms of hypothyroidism?
if they have normal TFTs
common causes of primary hypothyroidism?
Hashimoto’s thyroiditis (autoimmune disease)
iatrogenic (post surgery or radioactive iodine)
spontaneous atrophic
temporary thyroiditis
Derbyshire neck?
iodine deficiency leads to fall in T4 causing increase in TSH which stimulates hypertrophy (growth) of the thyroid gland
treatment of hypothyroidism?
levothyroxine (synthetic form of thyroxine)
once daily
half life is 7 days
100mcg (may be greater with heavier patients)
low T4 and high TSH is enough for diagnosis, no need for more tests
levothyroxine timing of dose?
take in early morning before breakfast
monitoring of hypothyroidism therapy?
annual TFTs once stable
if dose change, wait at least 6 weeks before repeating TFTs.
medications that impair levothyroxine absorption?
proton pump inhibitors (omeprazole/lansoprazole)
H2 antagonists (eg ranitidine)
iron, calcium, aluminium
don’t take T4 <4hrs after these
when might T4 requirement be increased?
if patient starts oestrogen (OCP/HRT) or anticonvulsants
OCP?
oral contraceptive pills
subclinical hypothyroidism TFT patterns?
TSH raised, FT4 normal
explanation for subclinical hypothyroidism TFT patterns?
TSH is more sensitive than FT4
T4 levels fall within normal reference range
TSH respond and increase out with normal reference range
main cause of subclinical hypothyroidism?
main cause is autoimmune chronic thyroiditis
weak evidence of adverse effects of subclinical hypothyroidism
lipids
BP
other CV risks
no hard evidence though
risk factors for hypothyroidism?
raised TSH and positive antibodies
secondary hypothyroidism TFT patterns?
low FT4, low TSH
what is secondary hypothyroidism caused by?
pituitary disease
