Thyroid disease Flashcards
What does a high TSH and a low T4 indicate?
- primary hypothyroidism
What does a low TSH with a high T4/3 indicate?
- primary hyperthyroidism
What would you measure and expect in TFTs for hyperthyroidism?
- T3, T4, TSH
- majority of cases are primary
- TSH will be reduced in most (unless rare case of TSH secreting tumour)
- most have raised T4 but ~1% have only raised T3
What would you measure and expect in TFTs for hypothyroidism?
- only T4 and TSH
- T3 adds no further info
- TSH varies throughout day (higher during darkness)
- so monitor at same time
What is sick euthyroidism?
- systemic illness
- TFTs may become deranged
- state of adaptation or dysreg of thyrotropic feedback control
- T4/T3 levels unusual even though thyroid normal
- TSH is either normal or low
- test should be repeated after recovery
- sick euthyroidism is caused by:
- fasting, starvation, stress
- sepsis, trauma, hypothermia
- malignancy
- heart failure, cardiopulmonary bypass, MI
- chronic renal failure, cirrhosis + DKA
Apart from the thyroid hormones, what other tests can be done to test thyroid function?
- thyroid autoantibodies - anti-TPO or thyroglobulin antibodies may increase in autoimmune disease (Grave’s or Hashimoto’s)
- TSH receptor antibodies - may be increased in Grave’s
- serum thyroglobulin
- ultrasound - for malignancy vs benign nodules
- isotope scan - malignancy, cause of hyper, retrosternal goitre, ectopic thyroid tissue, thyroid mets
Thyrotoxicosis is the clinical effect of excess thyroid hormone (hyperthyroidism), usually from gland hyperfunction.
What are the causes of hyperthyroidism?
- Grave’s disease
- toxic multinodular goitre
- toxic adenoma
- ectopic thyroid tissue
- exogenous
- subacute de Quervain’s thyroiditis
- pregnancy/post-partum
- TB
What are the symptoms of hyperthyroidism?
- weight loss (if v high there is a paradoxical weight gain)
- increased appetite
- heat intolerance
- irritability
- over-active
- sweats
- palpitations
- tremor
- labile emotions
- oligomenorrhoea +/- infertility
- rarely: psychosis, chorea, panic, itch, alopecia, urticaria
What are signs of hyperthyroidism?
- tachycardia/irregular pulse
- warm moist skin
- fine tremor
- goitre, thyroid nodules, bruit
- lid lag + retraction
- proximal myopathy
- chemosis
- palmar erythema
- systolic hypertension
- thin hair
- increased bone turnover
Graves’ disease is an autoimmune disease, characterised by oligoclonal IgG antibodies. It seems likely that some of these stimulate the thyroid by attaching to TSH receptors, while others stimulate the growth of soft tissue within the eye and yet others stimulate the skin causing pretibial myxoedema.
What are signs in Grave’s disease?
- eye disease - exophthalmos (proptosis is less extreme), opthalmoplegia, chemosis, lid retraction
- pretibial myxoedema - raised, oedematous purple-red lesions over anterolateral aspects of shins above lateral malleoli, non-pitting
- thyroid acropachy - extreme manifestation w/ clubbing, painful finger + toe swelling and periosteal rxn in limb bones
Grave’s disease has a characteristic triad of thyrotoxicosis, eye signs and a goitre.
What investigations would you do for a hyperthyroid patient?
- serum TSH -> should be low
- serum free T4 + T3 -> elevated
- serum microsomal + thyroglobulin abs -> in Grave’s
- Bloods -> inc ESR, inc Ca, LFTs
- thyroid ultrasound
- isotope scan
What would be the medical mangement for hyperthyroidism?
- beta-blockers to provide rapid symptomatic control
-
anti-thyroid meds ->
- carbimazole (SE: agranulocytosis)
- or carbimazole + thyroxine (less risk of iatrogenic hypo)*
*Treat and block means giving a high dose of carbimazole at the start and continuing this same high dose for the full 18-month period of medical therapy. This is effectively a medical thyroidectomy. “Block” alone would rapidly lead to hypothyroidism, with stimulation of TSH, which in turn would increase the size of the goitre. For this reason, the patient is “treated” with a standard dose of replacement thyroxine. The advantage of this approach is that the recurrence rate after treatment is slightly less and some patients seem to notice and improvement in their eye disease. This has led to the idea that carbimazole probably has two modes of action. The first occurs with low doses and depends on blocking thyroxine production within the thyroid follicular cell. With higher doses, the second effect, which somehow modulates the underlying immunological process, cuts in.
Radioiodine is another therapy for hyperthyroidism, what is a risk of this?
- safe, effective + cost-effective
- can develop hypothyroidism -> treated w/ lifelong thyroxine replacement therapy
- use in caution with active hyperthyroidism as can cause thyroid storm
- CIs: pregnancy, lactation
What is the surgical option for treating hyperthyroidism and when is it indicated?
-
thyroidectomy, if:
- failure of medical management
- large goitre
- patient choice
- intolerance of medication (eg rashes)
What are complications of subtotal thyroidectomy?
-
ACUTE, EARLY + RARE:
- bleeding
- thyroid crisis (hyperthermia, fast AF, pulm oedema)
-
DAMAGE TO LOCAL STRUCTURES:
- hypoparathyroidism - hypocalcaemia (chvostek’s, trousseau’s)
- damage to recurrent laryngeal nerve
-
COMMON, LATE:
- late hypothyroidism (30%)*
- recurrent hyperthyroidism (15%)*
*There is now a move towards total thyroidectomy w/ thyroxine replacement for all
What are the signs of hypothyroidism?
MLP BRADYCARDIC
- mental slowness
- loss of outer 3rd eyebrows
- peaches + cream complexion
- bradycardia
- reflexes relax slowly
- ataxia (cerebellar)
- dry thin hair/skin
- yawning / drowsy / coma
- cold peripheries
- ascites +/- non-pitting oedema +/- pericardial/pleural effusion
- round puffy face + ‘banana hands’ (myxoedema)
- deafeated demeanor
- immobile
- CF
