Hyper/Hypo - Thyroidism Flashcards
Where is TSH produced?
Anterior pituitary
How does T3 and T4 travel in the blood?
In the plasma bound to a protein, TBG
What is the structure of the thyroid gland?
Lies against and around front larynx and trachea, below thyroid cartilage
What is the majority of the thyroid hormone circulating in the blood?
T4
What protein is needed to make T3 and T4?
Tyrosine
What mineral is needed to make thyroid?
Iodine
Where is TRH produced?
Hypothalamus
Where are the receptors for T3 and T4?
In the nuclei of cells
What is the action of thyroid hormones?
- Increased BMR and heat production
Lipid metabolism - Lipolysis and beta oxidation
Carbohydrate metabolism - Stimulates insulin dependent entry of glucose into cells, increasing gluconeogenesis and glycogenolysis
Sympathomimetic - Increases response to catecholamines by increasing receptor number on target cells
What is the effect of thyroid hormone on the CVS?
- Increases heart response to catecholamines
- Increases CO by increasing HR and force of contraction
What is the effect of thyroid hormone on peripheral vasculature?
- Vasodilation to carry heat to body surface
What is the effect of thyroid hormone on the nervous system?
- Myelination of nerves
- Development of neurones
What thyroid function tests should you ask for if you suspect hyperthyroidism?
- T3 and T4
- TSH (all will have low TSH apart from TSH secreting pituitary adenoma)
What thyroid function tests should you ask for if you suspect hypothyroidism?
- T4
- TSH
T3 will not add any extra information
What is sick euthyroidism?
- TFT’s become deranged with systemic illness
What is TPOAbs? What is it testing?
TPOAbs - Thyroid peroxidase antibodies
- Increased in hypothyroid autoimmune thyroid disease
- If positive in Grave’s, there is an increased chance of developing hypothyroidism later on
What does TSH receptor antibody test for?
- Grave’s disease, raised
- Useful in pregnancy
What does serum thyroglobulin test for?
- Treatment of carcinoma
- Detection of self medicated hyperthyroidism if thyroglobulin is low
What is the use of ultrasound in thyroid disease?
- Can distinguish between cystic benign nodules and solid malignant nodules
When is a fine needle aspiration indicated?
- A solitary nodule
- Multinodular goitre
What is the use of an isotope scan?
- Useful to determine the cause of hyperthyroidism
- Finds retrosternal goitre
- Finds ectopic thyroid tissue
- Finds thyroid metastases with whole body CT
What patients should you screen for thyroid abnormalities?
- AF
- Hyperlipidaemia (hypothyroidism)
- Women with type I DM during 1st trimester and post delivery
- Amiodarone or lithium (biannually)
- Downs syndrome, Turners syndrome, Addisons disease (annually)
What are the symptoms of hyperthyroidism?
- Diarrhoea
- Weight loss
- Increased appetite (paradoxical weight gain in 10%)
- Overactive
- Sweats
- Heat intolerance
- Palpitations
- Tremor
- Irritability
- Labile emotions
- Oligomennorrhoea +/- infertility
What are the signs of hyperthyroidism?
- Pulse fast/irregular - AF/SVT
- Warm moist skin
- Fine tremor
- Palmar erythema
- Thin hair
- Lid lag
- Lid retraction
- Goitre
- Thyroid nodules
- Thyroid bruit