TBL - Thyroid and the adrenal axis Flashcards
Which hormone is first produced in response to low temperature and initiates an increase in metabolic rate?
Thyrotropin releasing hormone
What does thyrotropin releasing hormone stimulate the production of?
Thyrotropin
What is the role of thyrotropin?
Acts on the thyroid and stimulates the synthesis of thyroxine and triiodothyronine.
How does T3 initiate gene transcription?
T3 binds to the DNA bound thyroid hormone receptor with high affinity.
The receptor forms a heterodimer with the retinoid X receptor and transcription is initiated.
Low TSH, high FT4 and high FT3 would indicate what?
Hyperthyroidism.
Why is there low TSH is hyperthyroidism?
High T4 + T3 act as a negative feedback loop on the anterior pituitary gland, resulting in decreased levels of TSH.
What is the pathophysiology of Graves disease?
Autoantibody binds to TSH receptor of the thyroid epithelial cells resulting in stimulation of the gland, an over production of T4 (and subsequently T3) and hyperthyroidism.
What is the role of the capsule of the adrenal glands?
Acts as a central signalling centre that ensures replacement of damaged cells.
Which two medications are used to treat hyperthyroidism?
Carbimazole
Propylthiouracil
How long do patients need to wait to conceive after radioactive iodine treatment?
Females - 6 months
Males - 4 months
Why are patients who are taking long-term steroids at risk of adrenal crisis at times of infection?
Infection = stress on body. In times of stress, body produces more cortisol.
Synthetic cortisol long term use suppresses the bodies own ability to produce cortisol, so they will not increase their cortisol naturally.
If synthetic steroids are not increased in times of stress, the body will not have enough cortisol for its need, and is at risk of adrenal crisis.
