thyroid Flashcards
main cause of diffuse goitre
iodine deficiency
toxic multinodular goitre
where nodule develop on the thyroid gland that act independently of the normal feedback system + continously produce excessive thyroid hormone
2nd most common cause of thyrotoxicosis
toxic multinodular goitre presentation
most patients over 50
goitre with firm nodules
atrial fibrillation
patchy uptake on scintigraphy
high T3/T4
low TSH
toxic multinodular goitre treatment
radio-active iodine if significant hyperthyroid
surgery if structural problem or significant retrosternal extension
what are the 3 main embryological abnormalities associated with the thyroid?
failure to descend = lingual thyroid
excessive descent = retrosternal location in mediastinum
thyroglossal duct
how does the thyroid embryologically develop?
develops from evagination of pharyngeal epithelium
descent from foramen caecum to normal location
causes of hypothyroidism
hashimoto’s thyroiditis - commonest developed
iodine deficiency - commenest developing
medications - lithium + amiodarone
hypopituitarism = pituitary failing to produce enough TSH, caused by: tumours, infection, radiaation
incidence of hypothyroidism
higher in white populations
higher in areas of high iodine intake - too much inhibits
T3/4 + TSH levels in hyperthyroidism
TSH = low
t3/4 = high
T3/4 + TSH levels in primary hypothyroidism
TSH = high
T3/4 = low
T3/4 + TSH levels in secondary hypothyroidism
both LOW
hypothyroidism presentation
weight gain cold intolerance fluid retention - oedema, pleural effusion constipation coarse hair/loss psychosis, tendon jerks
management of hypothyroidism
levothyroxine
–> dose is titrated until TSH levels are normal - checked monthly until stable
if TSH is high - increase dose
myxoedema coma
severe hypothyroidism, medical emergency
women with long standing/untreated hypothyroidism
high mortality
presentation of myxoedema coma
bradycardia
heart block, T wave inversion
type 2 resp failure - hypoxia, resp acidosis
adrenal failure in some
hyperthyroidism presentation
anxiety + irritability sweating + heat intolerance weight loss fatigue loose stool
eyelid retraction
post-partum thyroiditis
transient thyrotoxic spike then falls + become hypothyroid
- course of about a year
- hypothyroid stage associated with postnatal depression
don’t treat thyrotoxicosis stage - would exacerbate fall to hypothyroid stage
hyperthyroidism management
anti-thyroid drugs - carbimazole (first line), propylthiouracil
radioactive iodine
beta blockers (symptommatic relief)
surgery
whats the first line anti-thyroid drug in treatment of hyperthyroidism in your average patient?
carbimazole
once patient has normal thyroid hormone levels, maintenance either-
> titration-block = dose titrated to maintain normal levels
> block + replace = dose is sufficient to block all production, takes levothyroxine titrated to effect
complete remission + ability to stop taking is usually <18months
whats the first line anti-thyroid drug in treatment of hyperthyroidism in 1st trimester of pregnancy?
propylthiouracil
small risk of hepatic reactions - including death
side effects of anti-thyroid drugs
allergic reactions - rash, urticaria
cholestatic jaundice
agranulocytosis
- highest risk in first 6 weeks
- warn patients verbally + in writing
- ATDs cannot be used again
radioactive iodine treatment in hyperthyroidism
single dose is taken up by thyroid gland + radiation destroys a proportion of thyroid cells (decreasing thyroid hormone production)
remission can take up to 6 months
patients can be left hypothyroid - levothyroxine for life
must not be pregnant within 6 months, avoid kids + pregnant for 3 weeks, limit contact with people for several days post dose
beta blockers in the treatment of hyperthyroidism
propranolol - non-selectively blocks adrenergic activity (not just heart) symptomatic relief only useful in thyrotoxicosis crisis block adrenalin related symtptoms **not in asthma**
symptomatic relief of choice in hyperthyroidism
propranolol
risks of surgery in hyperthyroidism
levothyroxine for life
risk of -
- recurrent laryngeal nerve palsy
- hypothyroidism
- hypoparathyroidism
management of thyrotoxic crisis
admit, ABCDE, monitor, treat as hyperthyroidism
may require fluid resus, anti-arrthymic medication + beta blockers
what is Graves disease?
where TSH receptor antibodies cause primary hyperthyroidism
most common cause of hyperthyroidism
autoimmune condition
10F:1M
30-40yrs
pathophysio of Graves disease
TSH receptor antibodies mimic TSH and stimulate TSH receptors on thyroid
(TSH receptor antibodies cause primary hyperthyroidism)
presentation of Graves (triad)
diffuse goitre - without nodules
exophthalmos = bulging of eye out of socket
pretibial myxodema = deposits of mucin under skin on shins
Graves disease investigations
low TSH
high T3/4
TSH receptor antibody positive
scintigraphy = high uptake
hypercalcaemia + high alaline phosphatase - Graves associated with osteoporosis
treatment of Graves disease
carbimazole
- usually normal thyroid function after 4-8weeks
- block + replace quicker
radioiodine = 1st choice for relapsed Graves
!! smoking cessation
Graves complications associated with pregnancy
infertility / ammenorhoea
spontaneous miscarriage
still birth
thyroid crisis in labour
transient neonatal thyrotoxicosis (in baby) - caused by TRAb antibodies crossing placenta
how to distinguish between hypermesis + hyperthyroidism?
should improve by 20weeks gestation
not TRAb positive
only treat if persists >20weeks
gestational hCG-associated thryrotoxicosis
hCG increases T4 levels
hCG causes hypermesis (N+V during pregnancy)
should improve by 20weeks gestation
management of gestational hCG-associated thyrotoxicosis
supportive/symptomatic managment - beta blockers if needed
low dose antithyroid drugs - wait as late as possible (baby failing to thrive, weight loss)
1st trimester = propylthiouracil - risk of liver toxicity to mother
2nd/3rd trimester = carbimazole
consequences of giving carbimazole during 1st trimester
embryopathy (when organogenesis occuring)
2nd/3rd trimester only
scintigraphy uptake in thyroiditis
low
causes of thyroiditis
hashimoto's - hypo de quervain's - hyper post-partum drug-induced - amiodarone, lithium radiation infection
sub-acute thyroiditis
females, 20-50yrs
may be triggered by viral infection - fever, neck tenderness
scintigraphy = low uptake
usually self-limiting (over months)
Hashimoto’s thyroiditis
gradual autoimmune destruction of thyroid tissue
commenest cause of hypothyroidism in DEVELOPED
may be preceded by transient hyperfunction (hashitoxicosis)
hashimoto’s thyroiditis presentation
may be preceded by transient hyperfunction (hashitoxicosis)
middle aged women - 45/60yrs
other autoimmune
**associated with HLA-DR3 + -DR5
initially causes goitre followed by atrophy of gland
may see progressive fibrosis within gland
hashimoto’s thyroiditis associated antibodies
antithyroid peroxidase (anti-TPO)
antithyroglobulin
hashimoto’s pathyophysio
CD8 T cells mediate destruction of thyroid epithelium
cytokine mediated cell death - recruited macrophages that may damage thyroid follicles
which carcinoma does hashimoto’s thyroiditis particularly increase the risk of?
B cell NHL (non-Hodgkin lymphoma) in thyroid gland
De Quervains thyroiditis
viral infection with signs of hyperthyroidism
- fever, neck pain, tenderness, dysphagia
- self-limiting - NSAIDs, maybe beta-blockers
hyperthyroid phase followed by hypothyroid phase as TSH level falls - negative feedback
post partum thyroiditis
transient thyrotoxic then falls + becomes hypothyroid - hypo stage assoc with postnatal depression
can persist up to a year
dont treat - would exacerbate fall to hypo stage
5% of all women + 25% of T1DM
post partum thyroiditis has increased incidence in what other condition?
type 1 diabetes
–> post partum thyroiditis occurs in 25%
sick euthyroid syndrome
low TSH + T4
hospital inpatients, changes reversible upon recovery of systemic illness
diagnosis = exclusion of hypothyroid
no treatment
what does a high TSH and low free T4 suggest?
subclinical hypothyroidism
- on their way to developing hypothyroidism, TSH is more sensitive and early marker of thyroid problems
most common malignant tumour of the thyroid
papillary (75-85%)
follicular (10-20)
medullary
anaplastic
which tumour variants come under the phrase differentiated thyroid cancer (DTC)?
papillary + follicular variants
“differentiated” features = good prognosis
most take up iodine + secrete thyroglobulin
lower incidence in afro-americans
more common in women
environmental causes of differentiated thyroid cancers
ionisng radiation - papillary carcinoma
iodine deficiency - follicular carcinoma
which thyroid tumour can secrete calcitonin?
medullary thyroid carcinoma
calcitonin can be used as a tumour marker
histology of medullary thyroid carcinoma
derived from C-Cells (parafollicular)
derived from neural crest, not thyroid tissue
types of medullary thyroid carcinoma
sporadic (70%) - solitary nodule
familial - bilateral/multicenteric
associated with multiple endocrine neoplasia (MEN) - very young patients, prophylactic thyroidectomy
investigations + treatment of medullary thyroid carcinoma
neck USS + FNA
basal serum calcitonin + CEA
treatment = total thyroidectomy
–> recurrence in 35%
thyroid lymphoma
females 70-80
rapid onset of mass in thyroid
rare, associated with hashimoto’s
diagnosis = biopsy Mx = steroid, chemo, radio
anaplastic carcinoma of the thyroid
undifferentiated + agressive tumours
rapid growth + involvement of neck structures
poor prognosis
elderly females
mutation strongly associated with anaplastic carcinoma
TP53
histology of papillary carcinoma
papillary projections + pale empty nuclei
histology of follicular carcinoma
microscopically capsular invasion
lymph node + haematogenous spead in papillary carcinoma?
lymph node metastisis
haematogenous spread = uncommon
lymph node + haematogenous spead in follicular carcinoma?
rarely lymphatic spread
haematogenous spread = bone, lung, liver
differences between papillary + follicular carcinoma
both = slow grow, good prognosis
papillary
- lymphatic spread
- young women
follicular
- spread to lung, liver + bones
- middle aged women
management of differentiated thyroid cancer
total thyroidectomy
radioiodine to kill residual cells
yearly thyroglobulin to detect early recurrent disease
suppress TSH
potential lobectomy in low risk group
what can be used as a tumour cell marker for differentiated thyroid cancer?
thyroglobulin (Tg)
follow up management of differentiated thyroid cancer
TSH + Tg every 6 months for first 5yrs then annually for next 5yrs - consider discharge after this
TSH lower level than normal (0.4-4)
thyroglubulin (Tg) levels - tumour cell marker
what is thyroglobulin?
protein precursor of T4/T3
made by thyroid follicular epithelium
can be used as a tumour cell marker for differentiated thyroid cancer
