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
