Clinical Thyroid Disease Flashcards
What are the 4 categories of thyroid disease?
Hyperthyroidism
Hypothyroidism
Goitre
Thyroid cancer
What is the thyroid hormone pathway (from hypothalamus to thyroid?
TRH released onto anterior pit gland
TSH released from AP gland to thyroid
T3 = tri-iodothyronine
T4 - thyroxine both are released from thyroid
Hypothyroid signs and symptoms ?
Everything slows down
Weight gain Lethargy Feeling cold Constipation Heavy periods Dry skin/hair Brady-cardia Slow reflexes
GOITRE
Symptoms of hyperthyroidism?
Weight loss Anxiety HEat intolerance Bowel frequency Light periods Palpitations Hyper-reflexia
GOITE
What will hormone levels be if it is 1y hypo-T? Where does the problem lie?
Raised TSH
Low FT4 and FT3
Thyroid gland
What will hormone levels be if it is 2y hypo-t
Low TSH
Low FT4 and FT3
Pit gland
What is subclinical hypoT? What will hormone levels look like here?
When the pit gland goes into overdrive to maintain normal FT3 and FT4 levels
Raised TSH and Normal FT4 and FT3
Prevalence of hypoT?
Commonest endocrine disease after diabetes
More common in women
Causes of 1y hypoT?
Congenital
or
Acquired
Describe the congenital causes of hypoT?
Can be developmental = agenesis/maldevelopment
Or due to dyshormonogenesis = trapping/organification/dehalogenase
What is dyshormonogenesis?
A rare condition due to genetic defects in the synthesis of thyroid hormones
Describe the acquired causes of hypoT?
Autoimmune - hashimotos
Iatrogenic
Chronic iodine deficiency
Post-subacute thyroiditis
Name some iatrogenic causes of hypoT?
Postop/post-radioactive iodine
External radiotherapy for head and neck cancers
Antithyroid drugs
Cause of 2y/3y hypothyroidism?
Pituitary or hypothalamic damage
Tumours
Post surgery etc
Investigations for hypothyroidism?
Look for levels of TSH/FT4
Auto-antibodies :TPO - thyroid peroxidase antibodies
FBC - MCV will be increased
Lipids - hypercholesterolaemia
Hypernatremia
Increased muscle enzymes
Hyperprolactinaemia
Treatment for hypothyroidism?
Levothyroxine (LT4) (T4 tablets) - 50mcg/day and increase after 2 weeks to 100mcg _ test regularly during this time to find perfect levels
After stabalisation organise annual check ups
There is also Liothyronine (T3)
Is there a benefit to taking both levothyroxine and liothyronine together?
No - best to just take levothyroxine
Half life of T4?
4 days
What situations should special consideration be taken in regards to treatment?
Ischaemic heart disease
Pregnancy
Post-partum thyroiditis
Myxedema coma
What special care should be taken if patient has ischaemic heart disease?
Start at a lower dose 25 mcg and increase cautiously - due to risk of precipitating angina
What special care should be taken if patient is pregnant? Why?
Need an increase in LT4 dose by about 25% and keep TSH in a lower normal range and FT4 in a higher normal range
Should treat subclinical if planning on getting pregnant
Because hypothyroidism linked to foetal loss and lower IQ
What special care should be taken if patient has post-partum thyroiditis?
You should trial a withdraw and measure TFTs in 6 weeks
What special care should be taken if patient has myxedema coma
This is a very rare emergency and you may need IV T3 steroids
What is myxedema coma?
Severe hypothyroidism leading to a decreased mental status, hypothermia and other symptoms connected to slowing of multiple organs
When should treatment for subclinical hypothyroidism be considered?
Consider treatment if TSH is above 10
Above 5 with +ve thyroid antibodies
Elevated TSH with symptoms
How should treatment be carried out in subclinical hypothyroidism?
Trial of therapy for 3/4 months and continue if symptomatic improvement
What is the risks of overtreatment in subclinical hypoT?
Afib
Osteopenia - Bone density that is lower than normal peak density but not low enough to be osteoporosis
Causes of goitre?
Physiological - puberty, pregnancy
Autoimmune - Graves, hashimotos
Thyroiditis
Iodine deficiency
Dyshormogenesis
Goitre types
Multinodular Diffuse - colloid and simple Cysts Tumours - adenoma, carcinoma, lymphoma Misc. - Sarcoidosis, TB
What risk does a solitary thyroid nodule carry?
Risk of a malignancy - 5%
Solitary thyroid nodule investigations?
TFTs Ultrasound Isotope scanning Fine needle aspiration Chest and thoracic inlet X-rays if there is large retrosternal extensions
When would ultrasound scanning be useful?
Useful for separating into benign or malignant
When would isotope scanning be used?
If low TSH - hot nodule
What is a cold nodule?
A non-functioning thyroid nodule
What are the types of thyroid cancer?
Differentiated
Anaplastic
Lymphoma
Medullary
What are the 2 differentiated cancers?
Papillary and follicular
Features of papillary?
Commonest
Is multi-focal, local spread to lymph nodes
Good prognosis
Features of follicular?
Usually a single lesion
Mets to lung/bone
Good prognosis of tumour is resectable
Management of differentiated thyroid cancer?
Prognosis is poorer compared to other thyroid disease
Treatment is a near total thyroidectomy
High dose radioiodine (ablative)
Long term suppressive doses of thyroxine
Follow ups with thyroglobulin and whole body iodine scanning following 2-4 weeks of thyroxine withdrawal
Is anaplastic cancer aggressive or not?
Aggressive and has poor prognosis - doesn’t respond to radio-iodine
External RT may be useful
Features of a lymphoma?
Rare
May arise from pre-exisiting hashimotos thyroiditis
Treatment - best is external RT combined with chemotherapy
Where does a medullary thyroid cancer arise from?
What is it associated with?
What hormone will be raised?
Treatment and prognosis?
Parafollicular C cells`
Associated with MEN 2 - phaeochromocytoma and hyperparathyroidism
Serum calcitonin is raised
Treatment - total thyroidectomy, there is NO role for radioiodine. Prognosis is variable
What are some 1y causes of thyrotoxicosis (hyperthyroidism)
Graves disease most common at 70%
Toxic multinodular goitre
Toxic adenoma
What are some 2y causes of thyrotoxicosis
Pituitary adenoma secreting TSH
When can their be thyrotoxicosis without hyperthyroidism?
Destructive thyroiditis
Excessive thyroxine administration (meds)
What can cause Destructive thyroiditis ?
Post-partum
Amiodarone induced
Subacute
Prevalance of graves?
2-3 per 1000 per year
More common in women
Graves features?
Autoimmune driven condition
Thyroid peroxidase antibodies and TSH receptor antibodies involved
What part of the Hx should be taken into special consideration if a patient presents with suspected graves?
Family history of concurrent autoimmune disease
Graves disease diagnosis?
Test for TSH - will be low
T3 and T4 will be high
Symptoms specific to graves?
Clubbing like features
Gynaecomastia
Bulging eyes
(Hyperthyroidism symptoms also)
Features of multi-nodular goitre?
Toxic nodules that secrete TH
Seen in elderly and iodine def. patients
Has a goitre but no graves disease and will not go into spontaneous remission
Features of subacute thyroiditis?
Also called de Quervain’s
Generally younger patients - less than 50
Viral trigger - enterovirus or coxsackie
Symptoms of subacute? Treatment?
Painful goitre with/without fever or myalgia. HAs an increased ESR
May need short term steroid and NSAIDs
What is the overall management plan for hyperthyroidism
Beta blockers
Anti thyroid drugs
Radioactive iodine
Surgery
What is the most commonly used anti thyroid med?
Carbimazole
How is carbimazole used?
2 ways - Titration or block regimens
Titration - start on a high dose and gradually reduce to the lowest dose that works
Block - block thyroid gland with a carbimazole then replace treatment with thyroxine before thyroid gland can recontinue
Both have a 50% cure rate and a 30£ hypothyroidism rate, but block has higher side effects
When would ATDs be used over the others?
Elderly
Cardiac complications
Unwilling for RAI
2 ways RAI/radioiodine is used?
HIgh dose ablative - 90% cure but 70% hypothyroidism
Variable calculated - 60-90% cure and less hypoTs
Risks of RAI?
High risk of hypothyroidism
Do patients usually choose ATD or RAI? What mode is usually given? When is it avoided?
ATD before RAI is tried
Usually gived as a high dose albative
Avouided in severe eye disease
What is subclinical HYPERthyroidism?
TSH is suppressed but there is normal FT3 and FT4
