tell me about the histological make up of the thyroid gland
its made of thyroid follicles
these are a single layer of cuboidal follicle cells surrounding a pool of colloid - a storage vessel really
scattered around there are also C cells which produce calcitonin
tell me about the production of thyroid hormone from thyroglobulin to proper hormone
follicular cells synthesis the protein thyroglobulin which is then secreted into and stored in the colloid
thyroperoxidase enzyme on the colloid surface catalyses the addition of iodine to the tyrosine residues of the thyroglobulin. when the signal arises these are endocytoses by the follicle cells which cleave the tyrosine from the thyroglobulin and then release the T4 hormone to the blood. thyroglobulin recycles back
what are the binding proteins of thyroid hormone
thyroxine binding globulin does the most of it, then transthyretin and albumin as well. iodine due to its non-polar nature mostly travels bound to proteins in the blood
when can we get increases in TBG and decreases
pregnant people, people on the pill, methadone, heroin, increases,
people on glucocorticoid or androgen therapy see decreases
this just means bound and total change, but the free will react to the change to stay the same, as long as the rest of the HPT axis is intact
what does thyroid hormone have to do with sex hormone binding globulin
it increases its production from the liver
what effects would SHBG changes in thyroid issues have
hyperthyroid in male there will be lower free testosterone so possible oestrogen effects and breast growth
hypothyroid in women can mean excess free testosterone creating menstrual irregularities
effects of thyroid hormone
CVS: increase CO, increase HR and SV, decrease TPR, increase systolic pressure
metabolism: increase BMR, increase O2 consumption, increase thermogenesis, increased protein turnover
neuro effects: responsible for wakefulness, memory, alertness, reflexes, maintain normal emotional tone
whats the action of carbimazole
inhibits the thyroperoxidase enzyme thereby preventing the production of thyroid hormone
why is radioactive iodine a treatment option for thyroid hyperactivity
the thyroid gland is so effective at concentrating iodine that it wont go anywhere else, the radioactive aspect then destorys part of the thyroid making it less hyperactive
when doing the radioactive iodine or any other thyroid lowering medication, what else drugs wise will we do
also give synthetic thyroid hormone incase we go too far the other way
symptoms of hyperthyroid
weight loss, face flushing, nervous, restless, insomnia, systolic hypertension, warm moist skin, hair loss, increased BMR, tachcardia, heat intolerance, brisk reflex, fine finger tremor
symptoms of hypothyroid
weight gain, puffiness of the face, thick tongue, lethargic, slow thinking, hypertension, coarse dry skin, dry brittle hair, decreased metabolic rate, slow pulse, cold intolerant, slow reflex
what sypmtoms of hyperthyroid do we see extra in graves
get pretibial myxoedema, exopthalmos
what is graves
autoimmune condition that sees antibodies mimic the effects of TSH on the thyroid gland
treatment of graves disease
carbimazole to prevent iodination of thyroglobulin, also give beta blocker for symptom control like the fast heart rate
what is thyroiditis
an inflammatory condition of the thyroid whereby the thyroid leaks all its contents at once
whats the pattern of symptomology of thyroiditis
there is a hyperthryoid as all the contents are released, then once all the contents are lost there is hypothyroid that is slow recover on its own
treatment for thyroiditis
this is transient inflammation of the thyroid and then recovery, so usually doesnt need intervention
what are some other causes of hyperthyroidism
toxic multinodular goitre, toxic thyroid adenoma, TSH secreting pituitary adenoma, exogenous thyroid hormone use
what would we see on the thyroid scan of graves and thyroiditis, and nodular and multinodular goitre
graves would be diffuse darkening, thyroiditis would be diffuse under activity,
single nodule would have one dark patch with everything else normal
toxic multinodular will have several areas of darkening
how does one diagnose the hyperthyroidisms
TSH, free and total T3/T4 and TPO antibodies - for graves.
then the radioactive iodine with thyroid scan, possibly thyroid ultrasound
in a primary hyperthyroidism and secondary what pattern of T3/T4 and TSH will we see
high T3/T4 low TSH
high T3/T4 high TSH
whats the pattern of T3/T4 and TSH in primay and secondary hypothyroidism
1 - low T3/T4 high TSH
2 - low TSH or TRH, low T3/T4
what is two causes of primary hypothyroid
hasimotos thyroiditis - where there is autoantibody blocking of TSH receptors
iodine deficiency - not enough I2 to make enough T3/T4
