Endocrine: Hypothyroidism Flashcards
what is hypothyroidism?
underproduction of the thyroid hormones:
- thyroxine (T4) and triiodothyronine (T3)
what causes hypothyroidism?
- Hashimoto’s Thyroititis
- Iodine Deficiency
- Secondary to Treatment of Hyperthyroidism
- medications e.g. lithium, Amiodarone
- pituitary gland is failing to produce enough TSH (secondary hypothyroidism)
what is secondary (central) hypothyroidism?
underproduction of thyroid-stimulating hormone (TSH) by the pituitary gland
what is sub-clinical hypothyroidism?
asymptomatic, mild thyroid failure, with normal levels of T4 and T3, and minimal elevation of TSH.
what is myxoedema?
Myxoedema coma is a rare severe form of hypothyroidism with multi-organ failure.
what are some risk factors for hypothyroidism?
- iodine deficiency
- female
- middle age
- family/personal history of autoimmune thyroiditis
- radiotherapy/ previous radio-iodine thyroid ablation (Graves’ disease)
- amiodarone use
- lithium use
what are some clinical features of hypothyroidism?
Weight gain Fatigue Dry skin Coarse hair and hair loss Fluid retention (oedema, pleural effusions, ascites) Heavy or irregular periods Constipation
what are some differentials for hypothyroidism?
- depression
- alzheimers
- anaemia
NB secondary and primary hypothyroidism may present as each other
What TFTs results would you expect with primary hypothyroidism?
High TSH but low T4 and low/normal T3
What TFTs results would you expect with secondary hypothyroidism?
Low/normal TSH, low T4 and low/normal T3
what investigations would you do to confirm a diagnosis of hypothyroidism?
Serum thyroid-stimulating hormone (TSH).
add free T4 for secondary
what is the treatment for hypothyroidism?
levothyroxine: 1.6 micrograms/kg/day orally adjust dose in increments of 12.5 to 25 micrograms to normalise TSH.
NB: may exacerbate angina
what are some complications of hypothyroidism?
The main complication of treatment is over-replacement of thyroid hormone, which increases the risk of osteoporosis and atrial fibrillation.
