Clinical Thyroid Disease Flashcards
starting in the hypothalamus and ending in peripheral tissues, briefly outline the path taken to release TH
Hypothalamus releases TRH - acts on the anterior pituitary which releases TSH - acts on thyroid gland which produces T3 and T4 - travels in blood stream to act on peripheral tissues
what keeps the hormone levels in a tight range
negative feedback control
what is hypothyroidism
when the thyroid is under active - i.e. does not produce enough TH
what is hyperthyroidism
when the thyroid is over active - i.e. produces too much TH
what are some typical symptoms of hypothyroidism
symptoms associated with low metabolism e.g.:
- weight gain
- lethargy/fatigue
- feeling cold
- constipation
- heavy periods
- dry skin/hair
- bradycardia
- slow reflexes
- low mood
- GOITRE
severe = puffy face, large tongue, hoarseness, coma
what are some typical symptoms of hyperthyroidism
symptoms associated with high metabolism e.g.:
- weight loss
- anxiety/irritability
- heat intolerance
- increased bowel frequency
- light periods
- sweaty palms
- palpitations
- hyperreflexia/tremors
- GOITRE
- thyroid eye symptoms/signs
what would the TSH and FT4&3 levels be like in PRIMARY hypothyroidism
raised TSH
low FT4&3
what would the TSH and FT4&3 levels be like in SUBCLINICAL hypothyroidism
raised TSH
normal FT4&3
what would the TSH and FT4&3 levels be like in SECONDARY hypothyroidism
low TSH
low FT4&3
what occurs in subclinical hypothyroidism to explain normal levels of FT4&3
also known as compensated hypothyroidism - thyroid gland can raise TSH enough on its own to make levels of FT4&3 normal even though TSH levels are elevated
what area is affected in primary hypothyroidism
the thyroid - causes can be autoimmune (hashimoto’s) or iodine deficiency in the diet
what area is affected in secondary hypothyroidism
the anterior pituitary
what is the prevalence of hypothyroidism in men and women
men - 0.1%
women - 1.9%
prevalence of congenital hypothyroidism
1 in 3500 births
what are the cases of primary Hypo
- congenital
2. acquired
what are the different causes of congenital primary hypo
- developmental - agencies/maldevelopment
- dyshormonogenesis - trapping/organification/dehalogenase
cretin = someone who is untreated for primary hypo from birth
what are the different causes of acquired primary hypo
- autoimmune thyroid disease
- Hashimotos
- atrophic - Iatrogenic
- post op/radioactive iodine
- external RT for head/neck cancers
- antithyroid drugs, amiodrone, lithium, interferon - chronic iodine deficiency
- post subacute thyroiditis
- post partum thyroiditis
what re the causes of secondary/tertiary hypothyroidism
pituitary/hypothalamic damage
- pituitary tumour
- craniopharyngioma
- post pituitary surgery/radiotherapy
- sheehans syndrome
- isolated TRH deficiency
what is sheehans syndrome
when a woman has a massive post part haemorrhage - can lead to hypothyroidism
what are the 2 main investigations for hypothyroidism
- TSH/FT4 levels in the blood
2. Autoantibodies - TPO (thyroid peroxidase antibodies)
what are other indicators to look for in hypothyroidism
- in a FBC - MCV raised (macrocytic anaemia)
- lipids - hypercholesterolaemia
- hyponatremia due to SIADH
- increased muscle enzymes, ALT, CK
- hyperprolactinaemia
what is the main treatment for hypothyroidism
- levothyroxine (T4 substitute) tablets
2. liothyronine (T3)
how is levothyroxine given
initial dose 50micrograms/day
- increase after 2 weeks to 100 micrograms
- increase dose until TSH normal (or FT4 in normal range in secondary)
when should you review a patient on levothyroxine
2 months after starting
- annual testing once stabilisation of TSH met
what are special situations that call for a change in treatment and how would you treat them
- ischaemic heart disease - start lower dose (25mcg) and increase cautiously - RISK OF PRECIPITATING ANGINA
- pregnancy - patients need increase in LT4 dose
- Postpartum thyroiditis - trial withdrawl and measure TFTs in 6 weeks
- myxedema coma - very rare emergency, may need IV T3 (steroid)
when would you treat subclinical hypo
- consider treatment when TSH >10
- TSH > 5 with positive thyroid antibodies
- TSH elevated with symptoms - trial therapy for 3/4 months - continue if symptomatic improvement
what are the risks of over treatment
- osteopenia
- atrial fibrillation
- excitability
what is goitre
the enlargement of the thyroid gland - swollen neck
what are the cases of goitre
- physiological - puberty/pregnancy
- autoimmune
- thyroiditis
- iodine deficiency
- dyshormogenesis
- goitrogens - eg cabbage
what are the different types of goitre
- multinodular
- diffuse - colloid, simple
- cysts
- tumours - ademona, carcinoma, lymphoma
- miscellaneous - sarcoidosis, tuberculosis
when is a solitary nodule at risk of malignancy
- in children
- adults less than 30 or over 60
- previous head and neck irradiation
- pain, cervical lymphadenopathy
*large dominant nodule of MNG also needs investigation
what are the investigations for a solitary thyroid nodule
- thyroid function tests (toxic nodule)
- isotope scanning (hot nodule)
- Ultrasound - differentiating malignant from benign
- Fine needle aspiration
- X-rays
what is a hot nodule
an autonomous functioning nodule - on isotope scan shows up bright = area of activity - i.e. iodine isotope uptake normal, TSH doing its job
what is a cold nodule
a non-funtioning thyroid nodule - ie a cyst or part of gland that is not taking up anything
what are the 5 types of thyroid cancer
MAIN ONES:
- papillary
- follicular
OTHER:
- anaplastic
- lymphoma
- medullary
what are the features of papillary thyroid cancer
- most common
- multifocal, local spread to lymph nodes
- good prognosis
what are the features of follicular thyroid cancer
- usually single lesion
- metastases to lung/bone
- good prognosis if resectable
what are the features of anaplastic thyroid cancer
- <5% of thyroid cancers
- aggressive, locally invasive
- very poor prognosis
- does not respond to radio iodine BUT external RT may help briefly
what are the features of lymphoma
- rare
- may arise from preexisting hashimotos thyroiditis
- external RT more helpful, combined with chemotherapy
what are the features of medullary thyroid cancer
- tumour arising from parafollicular C cells
- often associated with MEN 2
- serum calcitonin levels raised
- total thyroidectomy needed, no role for radio iodine
- variable prognosis
what factors make prognosis poorer
- age - <16 or >45
- tumour size
- spread outside thyroid capsule
- metastases
- TNM stage
what is the treatment for process for thyroid cancer
- near total thyroidectomy - remove everything you can including associated lymphs
- ablative therapy - radioactive iodine - gets easily picked up by thyroid
- long term thyroxine to suppress tumour - “puts tumour to sleep” - doesn’t need to “wake up” and produce hormone as hormone levels synthetically high enough
