Thyroid Disease Flashcards
What term us used to describe normal thyroid function?
- eu = normal
- thyroid = thyroid
- euthyroid
What does the term thyrotoxicosis relate to?
- toxic levels of thyroid hormones in the circulation
What is the difference between thyrotoxicosis and hyperthyroidism?
- thyrotoxicosis = increased levels of thyroid hormones in circulation
- hyperthyroidism = increased secretion of thyroid hormones from thyroid gland
What does the term goiter refer to in relation to the thyroid gland?
- abnormal growth of the thyroid gland
Hypothyroidism is a low production of thyroid hormones and can be separated into primary and secondary. What is primary and secondary hypothyroidism?
- primary = issue with thyroid gland not secreting sufficient thyroid hormones
- secondary = issue with hypothalamus and/or pituitary gland
Which vertebrae does the thyroid gland align with?
- C5 -T1
Which cartilage does the thyroid gland wrap around in the neck region?
- cricoid cartilage
Label the image below using these labels:
- thyroid cartilage
- cricoid cartilage
- right lobe of thyroid gland
- isthmus
- left lobe of thyroid gland
- trachea
1 - cricoid cartilage 2- right lobe of thyroid gland 3 - trachea 4 - isthmus 5 - left lobe of thyroid gland 6 - thyroid cartilage
In order for thyroid hormones triodothyronine (T3) and thyroxine (T4) to have an affect at tissue throughout the body there are 3 stages of the positive feedback loop. These are essentially the stages that result in T3 and T4 being secreted and reaching the target tissue. What are the 3 stages?
1 - hypothalamus signals the pituitary gland
2 - pituitary gland signals the thyroid gland
3 - triiodothyronine (T3) signalling in tissue and thyroxine (T4) signalling in the circulation
There are 3 common thyroid tests that are conducted, namely thyroid stimulation hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4). What are the normal levels of TSH secretion?
- 0.3 - 3.5 mU/L
There are 3 common thyroid tests that are conducted, namely thyroid stimulation hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4). What are the normal levels of FT4 secretion?
- 10 - 25 pmol/L
There are 3 common thyroid tests that are conducted, namely thyroid stimulation hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4). What are the normal levels of FT3 secretion?
- 3.5 - 7.5 pmol/L
Thyroid peroxidase (TPO) is an enzyme expressed mainly in the thyroid where it is secreted into colloid. TPO oxidizes iodide ions to form iodine atoms and then allows the formation of thyroxine (T4) or triiodothyronine (T3) through the addition of iodine molecules. What is the TPO autoantibody?
- assessment if TPO antibodies are present
- TPO antibodies are not present in healthy thyroid
- if TPO antibodies are present suggest autoimmune disease (commonly hypothyroidism)
What is the purpose of thyroid stimulating hormone (TSH) antibody (TRAB) test?
- test to assess if patients have antibodies against against the TSH receptor on thyroid gland
- healthy thyroids do not have the antibodies
- may indicate an autoimmune disease
When observing a thyroid stimulating hormone (TSH) curve, what can low levels at the end of the curve, observed in the image below suggest in the patient?
- thyroid autoantibodies (antibodies that recognise your own tissue and incorrectly target this)
- may present as thyroid disease
When measuring thyroid stimulating hormone (TSH) in a clinical setting, what are the 2 main limitations?
1 - TSH is slow to respond due to pathological changes, so acute not the best measure
2 - TSH test assumes no pituitary pathology, so T3 and T4 need to be tested alongside
Thyroid peroxidase (TPO) is an enzyme expressed mainly in the thyroid where it is secreted into colloid. TP oxidizes iodide ions to form iodine atoms and then allows the formation of thyroxine (T4) or triiodothyronine (T3) through the addition of iodine molecules. Does a negative TPO autoantibody test and TRAB-TSH (receptor autoantibody) rule out thyroid autoimmune disease?
- no, TPO antibodies are intracellular marker making them difficult to measure
- CAN be a marker of autoimmune disease and suggest an increased risk of immune disease
- a positive test will confirm a diagnosis though
Are the antibodies that are created against thyroid peroxidase (TPO) and TRAB-TSH (receptor autoantibody) always destructive?
- no they can be destructive or stimulatory
Hypothyroidism is a lack of thyroid hormones and can be primary (thyroid related) or secondary (hypothalamus/pituitary gland) related. Does hypothyroidism always present with symptoms?
- no
- may be no symptoms
Hypothyroidism is a lack of thyroid hormones and can be primary (thyroid related) or secondary (hypothalamus/pituitary gland) related. What are the 6 most common and severe symptoms that patients with hypothyroidism may present with?
1 - cold intolerance 2 - facial puffiness 3 - dry skin 4 - hair loss 5 - hoarseness 6 - heavy menstrual periods (impaired ovarian follicular development)
Hypothyroidism is a lack of thyroid hormones and can be primary (thyroid related) or secondary (hypothalamus/pituitary gland) related. The 6 most common and severe symptoms that patients with hypothyroidism may present with include:
1 - cold intolerance 2 - facial puffiness 3 - dry skin 4 - hair loss 5 - hoarseness 6 - heavy menstrual periods
What are the 2 most severe signs, not included above, that in extreme cases patient with hypothyroidism can experience?
- bradycardia
- coma or stupor (near unconsciousness)
In a patient with primary hypothyroidism, why might we see elevated thyroid stimulating hormone (TSH) and lower levels of thyroxine and triiodothyronine (T3)?
- thyroid has reduced T3 and T4 secretion
- low T3 and T4 means reduced negative feedback to hypothalamus and pituitary gland
- hypothalamus and pituitary gland increase stimulation of thyroid through TRH and TSH
What are some of the most common causes of primary hypothyroidism (affecting the thyroid directly)?
- autoimmunity (among most common in UK)
- infection (thyroiditis)
- drug interactions
- congenital hypothyroidism
- iodine deficiency
- post hyperthyroidism treatment
In a patient with secondary hypothyroidism (affecting the hypothalamus or pituitary gland), why might we see low levels of thyroid stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3)?
- hypothalamus may reduce thyrotropin levels (TRH) and/or pituitary gland may reduce secretion of TSH
- lower levels of TSH means less T3 and T4 will be released from the thyroid
If a patient presents with high levels of thyroid stimulating hormone and lower levels of thyroxine (T4) is this likely to be a primary or secondary hypothyroidism disorder and what blood test can be performed to confirm this?
- primary
- thyroid autoantibodies (TPO or TSH receptors) blood tests
- Hashimoto disease is the most common autoimmune disease
What is the key treatment approach for a patient with hypothyroidism?
- increase thyroxine (T4)
- ensure thyroid stimulating hormone (TSH) levels remain at normal levels