Thyroid Disorders Flashcards
Describe where the thyroid gland is located and its anatomy?
-Thyroid gland is located at the back of the tongue.
Located in the neck and it is shield shaped.
It has a left lobe, right lobe and an isthmus in the middle.
what is the pyramidal lobe?
It is part of the extension from the back of the tongue from which the thyroid originated.
where are the parathyroid glands and what are they involved with?
Found embedded at the four corners of the thyroid, these parathyroid glans are involved in the control of calcium.
What is the name of the dimple at the back of the tongue and what caused the formation of that structure?
Foramen Caecum
This is a remnant left by the descending thyroglossal duct.
What is the weight and dimensions of a normal thyroid gland?
20 g
4 cm x 2.5 cm x 2.5 cm
Which lobe of the thyroid is the biggest?
RIGHT > left
What nerves run near the thyroid gland and what does it supply?
Recurrent laryngeal nerves.
-innervates the larynx (voice box) allowing speech.
Describe the embryological development of the thyroid gland?
Origin: midline outpouching of the floor of the pharynx ( base of the tongue is the origin)
Outpouching forms a duct which elongates down- thyroglossal duct.
It migrates down the neck and divides into 2 lobes.
-usually the thyroglossal duct disappears leaving only a dimple at the back of the tongue called the foramen caecum.
The thyroid gland then develops.
What are three problems that can occur with the development of the thyroid?
AGENESIS - complete absence of the thyroid
INCOMPLETE DESCENT - it my not descend to the correct point in the neck. This can cause problems with delivery.
THYROGLOSSAL CYST - thyroglossal duct persists and cysts may form years later.
What is lingual thyroid?
Thyroid tissue barely descends at all and remains very close to the back of the tongue which can cause breathing difficulties.
What is cretinism?
Irreversible brain damage caused by a lack of thyroxine
State two features of cretinism.
Stunted growth
Low IQ
How are newborns tested for cretinism and what is the treatment?
Heel-prick test
TSH is measured and if it is ABNORMALLY HIGH then they are given THYROXINE
What other disease does the heel-prick test ?
The Guthrie Test for phenylketonuria.
where is thyroxine synthesised and what is the role of the thyroid gland?
Thyroid follicular cell is the site of thyroxine synthesis. Thyroxine affects basal metabolic rate and every cell is controlled by thyroxine.
Role of the thyroid gland:
- responsible for the synthesis, storage and secretion of thyroid hormones.
- these hormones regulate growth, development and basal metabolic rate
Is thyroid disease more common in males or females?
Females
Female: Male ratio = 4:1
Define myxoedema.
Primary Hypothyroidism - primary thyroid failure
What is the most common cause of primary thyroid failure?
Autoimmune damage to the thyroid
How do TSH levels change in primary thyroid failure?
TSH levels rise to try and stimulate and increase in thyroxine production
(eventually the TSH production will become exhausted and it will decline)
What exerts negative feedback on TSH and TRH release?
T3/T4 - direct negative feedback on the pituitary gland to inhibit more production of TSH and indirect negative feedback on the hypothalamus to inhibit production of TRH.
State some features of primary hypothyroidism.
EVERYTHING SLOWS DOWN Deepening voice Depression and tiredness Bradycardia Cold intolerance Weight gain and reduced appetite Constipation Heart enlargement
What is the treatment for hypothyroidism and what happens if left untreated?
Give THYROXINE daily and monitor TSH.
-death due to rise in cholestrol which increases risk of death from heart attacks and strokes.
How does TSH change in hyperthyroidism/thyrotoxicosis?
TSH is low because the elevated Thyroxine exerts a powerful negative feedback effect on it
TSH falls to zero.
State some features of hyperthyroidism and the clinical symptoms of this?
Raised metabolic rate Raised temperature Lose weight + burn up calories Tachycardia Clinical: diarrhoea, myopathy, mood swings, palpitations, feeling hot in all weather, goitre/sore eyes
What is a common cause of hyperthyroidism?
Graves’ Disease
What causes Graves’ disease?
The whole thyroid gland is SMOOTHLY ENLARGED and the whole gland is OVERACTIVE
Caused by the immune system producing an antibody that MIMICS TSH
Other than an increase in thyroxine production, state 3 other features of hyperthyroidism.
GOITRE - enlargement of the thyroid could form a goitre
EXOPHTHALMOS - other antibodies could bind to the eye muscles pushing the eye forwards
PRETIBIAL MYXOEDEMA - other antibodies could promote growth of soft tissue on the SHIN
