Thyroid Gland and Its Disorders Flashcards
what shape is the thyroid gland?
butterfly consisting of right and left lobe joined by narrow isthmus
where is the thyroid gland?
in the neck, over the trachea
how much does thyroid gland weight?
15-20 grams with parathyroid glands at the back
what two hormones are produced by the thyroid gland?
T3 - thyroxine
T4 - triiodothyronine
what are endocrine organs controlled by?
hypothalamo-pituitary axis
what is the hypothalamo-pituitary axis?
Hypothalamus releases TRH which stimulates anterioir pituitary to release TSH which stimulated thyroid gland to synthesise and release T3/T4 and then you get negative feedback to stop TSH/TRH
what are primary problems?
issues with the gland itself
what are secondary problems?
issues with the pituitary
what does the thyroid gland release more of?
T4
which hormone is more active?
T3
where can T4 be converted into T3?
the liver and in specific target tissues as heart requires diff amount of T3 compared to brain etc
what is thyroid gland made up of?
thyroid follicles
what are thyroid follicles made up of?
mass of colloid surrounded by follicular cells
what do follicular cells do?
produce thyroid hormone
what are para-folicular cells (C Cells)?
produce calcitonin involved in calcium metabolism
what is a colloid?
contains thyroglobulin, a protein synthesised by the follicular cells
what is thryoglobulin?
contains tyrosine residues that get combined with iodine to allow formation of thyroid hormones
what is reverse T3?
inactive
Tyrosine + Iodine
Monoiodotyrosine (MIT)
Monoiodotyrosine + Iodine
Diiodotyrosine (DIT)
MIT + DIT
T3
DIT + DIT
T4
how do most circulating thyroid hormones travel in circulation?
bound to plasma proteins
what are 70% of the bound thyroid hormones bound to?
Thyroid binding globulin
what are 10-15% of the bound thyroid hormones bound to?
transthyretin
what are 20-15% of the bound thyroid hormones bound to?
albumin
what are two types of thyroid disease?
diffuse disease and nodular disease
what is enlargement of the thyroid gland?
goitre.
what is a uniformly swollen thyroid gland?
diffuse goitre
what is a lumpy swollen thyroid gland?
nodular goitre
what is hyperthyroidism?
too much thyroid hormone so metabolism speeds up
what is hypothyroidism?
too little thyroid hormone so metabolism slows down
signs of hyperthyroidism
weight loss, anxiety, palpitations, diarrhoea, hyperactivity, tremor, tachycardia, exopthalamose (bulging eyes)
who is hyperthyroidism more common in?
women
what are causes of thyrotoxicosis?
auto-immune so Grave’s disease or toxic multi nodular goitre. Or follicular thyroid cancer
how will a Graves patient present?
smooth goitre and exopthalamos
more eyes signs of graves
periorbital oedama, chemosis, lid retraction, proptosis, opthalmoplegia
Diagnosis of primary hyperthyroidism
suppressed TSH, elevated thyroid hormones
how is hyperthyroidism diagnosed?
isotope uptake can be used, thyroid ultrasound and TSHr antibody levels
how is hyperthyroidism treated?
antithyroid medications like carbimazole, methimazole and propylthiouracil. beta blockers help patient feel better
what do antithyroid medications do?
block TPO enzymes (thyroid peroxidase)
hypothyroidism clinical features?
fatigue, cold intolerance, weight gain, bradycardia, constipation
what is the most common cause of hypothyroidism in iodine sufficient areas?
Hashimotos disease as antibodies are directed toward TPO or thyroglobulin.
who is hypothyroidism more common in?
females
what form of hypothyroidism is hashimotos?
primary
what are other causes of hypothyroidism?
post-thyroidectomy or post RAI, iodine deficiency/excess and drugs
how is hypothyroidism investigated?
TPO antibody levels, note low T4 and high TSH
how is hypothyroidism treated?
given missing hormone in form of levothyroxine
what is the opposite of thryoid storm?
myxoedema coma
what is myxoedema coma caused by?
long standing untreated hypothyroidism, MI, cold exposure or sedative drugs.
what does myxoedema lead to?
decreased mental status, hypothermia
what is hashimotos thyroiditis?
painless, diffuse goitre
what is post-partum thyroiditis?
after delivery of baby
who is hypothyroidism more common in?
females
what form of hypothyroidism is hashimotos?
primary
what are other causes of hypothyroidism?
post-thyroidectomy or post RAI, iodine deficiency/excess and drugs
how is hypothyroidism investigated?
TPO antibody levels, note low T4 and high TSH
how is hypothyroidism treated?
given missing hormone in form of levothyroxine
what is the opposite of thryoid storm?
myxoedema coma
what is myxoedema coma caused by?
long standing untreated hypothyroidism, MI, cold exposure or sedative drugs.
what does myxoedema lead to?
decreased mental status, hypothermia
what is hashimotos thyroiditis?
painless, diffuse goitre
what is post-partum thyroiditis?
after delivery of baby
what is subactue?thyroiditis?
painful thyroiditis, anyone can have it
what is acute thyroiditis?
bacteria, fungus
what is euthyroidism?
normal thyroid function
what is dysphagia?
difficulty swallowing
what is dysphonia?
inability to produce sounds
what is dyspnoea?
breathless
name a few types of thyroid cancer?
papillary thyroid carcinoma, follicular carcinoma, anaplastic carcinoma, lymphoma
how is thyroid cancer investigated?
- comes in with thyroid lump
- find out if symptoms are hyper or hypo
- decide if diffuse or nodular goitre
- do thyroid blood test to find out if eu/hypo/hyper thyroid
- FNA (fine needle aspiration) cytology and look at some cells
