Thyroid and Parathryoid disease Flashcards
What are the hormones responsible serum Ca2+ and PO4- levels? What is their role?
Vit D - increase
PTH- increase
Calcitonin - decrease
What are the various forms of vit D found and where do the conversions happen?
Cholecalciferol (converted in the liver to) calcidiol
Calcidiol (converted in the kidney to) calcitriol
Calcitriol is the activated form of vitamin D
What effect does low serum Ca2+ levels have on the parathyroid gland?
Stimulates PTH and decreases calcitonin
What is the effect of PTH on the body?
It stimulates bones to release Ca2+ and PO4-
It stimulates the kidney to convert calcidiol to calcitriol and increases reabsorption from tubules
What effect does Vit D have on the body?
It stimulates the bones to release Ca2+ and PO4-
It stimulates reabsorption of Ca2+ from the nephrons
It stimulates absorption of Ca2+ from the gut
It negatively feedbacks to the parathyroid gland to prevent PTH release
Give some causes of high Ca2+ (7)
High osteoclasts activity High PTH High PTHrP Drugs Endocrinopathy High vitamin D action
In what situations might you get increase osteoclasts activity?
Metastic cancer to bone
Paget’s disease
Immobility
What would cause raised PTH?
Primary hyperparathyroidism
Why might there be high levels of PTHrP
Malignancy
What drugs cause raised serum calcium?
Thiazides
Lithium
Excess dietary Ca2+
Give some examples of endocrinopathies that cause raised calcium levels
Raised T4 (hyperthyroidism)
Addison’s disease
Phaeochromocytoma
What would cause a raised Vit D level ?
Excess dietary vit D
Sarcoidosis
What action does T3 and T4 have on the body?
Increase cell metabolism via nuclear receptors and are thus vital for growth and mental development
Also increase catecholamine effects
When might total T3/4 levels be raised and why?
When thyroxine binding globulin (TBG) is high
This can rise in pregnancy, oestrogen therapy (HRT, contraception) and hepatitis
When might total T3/T4 be low due to TBG and not the true values?
Nephrotic syndrome, Malnutrition (protein loss)
Drugs (androgens, corticosteroids, phenytoin)
Chronic liver disease
Acromegaly
In what situations would you want to screen for thyroid dysfunction?
- AF
- hyperlipidaemia (up to 14% have hypothyroidism)
- diabetes (annual review)
- women with T1DM during T1 of pregnancy and post delivery
- pt on amiodarone and lithium (6 monthly)
- pt with Down’s or Turner’s syndrome or Addison’s disease (yearly)
What is thyrotoxicosis?
Clinical effect of XS thyroid hormone, usually from gland hyperfunction
What are the symptoms of thyrotoxicosis?
Diarrhoea Reduced weight Increased appetite Heat intolerance Sweating Palpitations Tremor Irritability Oligomenorrhoea
What are the signs of thyrotoxicosis?
Tachycardia (AF) Warm moist skin Fine tremor Palmar erythema Thin hair Lid retraction Potentially a goitre
What are some specific signs of Graves’ disease?
Eye disease (exophthalmos) Pretibial myxoedema (lipopolysaccharides deposits in the skin causing swelling) Thyroid acropachy (clubbing)
What tests would you do in suspected thyrotoxicosis? What would be the expected results?
TFT: low TSH, high T4,T3 FBC: mild normocytic anaemia, raised ESR U+E: raised Ca2+ LFT: raised Thyroid autoantibody screen
What are the causes of thyrotoxicosis?
Graves’ disease: IgG autoantibodies binding to and activating thyrotropin receptors- causing thryoid enlargement and increased hormone production
Toxic multinodular goitre: seen in elderly/iodine deficient areas. Nodules secreting T3/4. Surgery may be needed for compressive symptoms of enlarged gland
Toxic adenoma: solitary nodule secreting T3/4
Ectopic thyroid tissue: potentially ovarian teratoma
Exogenous: iodine XS, levothyroxine XS, decreased TBG
How do you treat thyrotoxicosis?
- Drugs: Beta blockers for symptoms and antithyroid medications ie carbimazole
- Radioiodine: CI: pregnancy/lactation
- Thyroidectomy: usually total, risks of hoarse voice+ hypoparathyroidism
What is the worrying side effect of carbimazole?
Agranulocytosis, reduced neutrophils
Can lead to neutropenic sepsis
