general Flashcards
define hyperthyroidism
excess of circulating thyroid hormones (thyrotoxicosis), which are produced by an overactive thyroid gland
describe the difference between primary (most common), secondary hyperthyroidism (rare)
primary = cause is in the thyroid gland itself e.g. Graves disease (TSH receptor antibodies) or toxic thyroid nodules or malignancy
secondary = cause is elsewhere e.g. the abnormal stimulation of a normal thyroid gland by TSH-secreting pituitary tumour
describe thyrotoxicosis without hyperthyroidism
thyrotoxicosis without thyroid gland over-activity e.g. from drugs (levothyroxine) or thyroiditis
how is the amount of thyroid hormone in the bloodstream controlled?
negative feedback
stimulus (e.g. low levels of thyroid hormones in the blood) needed to send signal to hypothalamus –> secretes TRH –> ant. pituitary –> secretes TSH –> via bloodstream to thyroid gland –> thyroid hormones into bloodstream. if there are normal levels of thyroid hormones in the blood –> negative feedback to the ant. pituitary to stop secretion of TSH (also some -ve feedback onto hypothalamus)
list common signs/symptoms of hyper and hypo-thyroidism
hyperthyroidism:
- weight loss
- tremor
- heat intolerance
- palpitations
- sweating
- peripheral vasodilation
- tachycardia
hypothyroidism:
- constipation
- weight gain
- dry hair and skin
- cold intolerance
- slow-relaxing reflexes
most cases of primary hyperthyroidism are attributed to an autoimmune mechanism. However, some cases are caused by malignancy. describe the characteristics of a thyroid tumour and the potential risk factors for malignancy
- large, rapidly growing hard/fixed mass. usually associated with lymphedema in the neck
- risk factors = FHx of malignancy, Hx of ionising radiation in the head/neck, male, age <20 or >60
what is the first step of diagnosis hyperthyroidism? What other investigation may be necessary?
- 1st bloods
- ultrasound scan if any lumps identified
thyroid storm (thyrotoxic crisis) is a complication of hyperthyroidism and is potentially life-threatening. what is the clinical presentation of this condition?
exaggeration of usual physiological response seen in hyperthyroidism and can occur after trauma, childbirth, surgery, infection or stroke in people with untreated or poorly controlled hyperthyroidism: tachycardia, fever, AF, HF, fever, diarrhoea, jaundice, agitation, delirium and coma
when should you refer someone with hyperthyroidisms to endocrinologist?
admit as a medical emergency a person with symptoms of thyroid storm
refer using a suspected cancer pathway (app. within 2 weeks) is person has thyroid nodule or goitre and malignancy is suspected
refer all others with overt hyperthyroidism, urgency depending on clinical judgement, for further Ix and management
describe how you would interpret TFT results to diagnose hyperthyroidism
includes TSH, free thyroxine (fT4) and free triiodothyronine (fT3)
- TSH is usually the most useful. will be low because of -ve feedback mechanisms
- a low TSH and high fT4 is consistent with hyperthyroidism
list the differences between aetiologies of a benign and malignant thyroid nodule
benign: colloid nodule, adenoma focal thyroiditis, thyroid cyst, benign lymph node hypertrophy, parathyroid cyst
malignant: papillary, follicular, medullary and anaplastic thyroid carcinoma; lymphoma or metastasis to thyroid
what percentage of thyroid nodules contain cancerous cells?
5%
what medication can be offered at low dose (can be increased if necessary) to help improve symptoms of hyperthyroidism while patient waits for endocrinologist appointment? what are the 4 major contraindications?
propranolol (B-blocker) to provide relief from adrenergic symptoms, particularly anxiety and tachycardia
CI’s:
- asthma
- uncontrolled HF
- marked bradycardia
- hypotension
what are the 5 questions pt’s should be asking to take more control of their healthcare -> realistic medicine!
- need
- benefit
- risks
- choice
- if I don’t?
beta blockers can only help symptoms of hyperthyroidism, not the underlying cause. what are the 3 options for long term management of the underlying cause of hyperthyroidism?
- anti-thyroid drugs
- radioiodine
- surgery