Endocrine - Thyroid Function Tests Flashcards
What is used as a screening test for thyroid disease?
TSH
If TSH levels are abnormal what is measured to look at the thyroid?
T3
(Triiodothyronine)
T4
(Thyroxine)
What is primary hyperthyroidism?
Thyroid produces excessive thyroid hormones
TSH suppressed by high T3 and T4
What is secondary hyperthyroidism?
Pituitary adenoma causing excessive TSH production
TSH, T3,T4 all raised
What is primary hypothyroidism?
Inadequate production of T3 and T4 by the thyroid
High TSH from pituitary to increase circulating T3 and T4
What is secondary hypothyroidism?
Pituitary produces inadequate TSH, under stimulation of thyroid
Low T3,T4 and TSH
Complete the table
What are the different antibodies which affect the thyroid?
Anti-thyroid peroxidase (anti-TPO) antibodies
Autoimmune thyroid disease
- Grave’s disease
- Hashimoto’s thyroiditis
Anti-thyroglobulin (anti-Tg) antibodies
- Grave’s disease
- Hashimoto’s thyroiditis
- Thyroid cancer
TSH receptor antibodies
Autoantibodies that mimic TSH, bind to TSH receptors to stimulate thyroid hormone release
- Grave’s disease
What imaging is used to investigate thyroid nodules?
Ultrasound
Distinguishes between cystic and solid nodules
Can also be used to guide biopsy
What is used to investigate hyperthyroidism and thyroid cancer?
Radioisotope scans
Radioactive iodine given orally or IV
Iodine is used by thyroid cells to produce T3 and T4
More active thyroid cells means radioactive iodine is taken up faster
Gamma camera detects gamma rays emitted from radioactive iodine
What does different uptake in radioisotope scans mean?
Diffuse high uptake
Grave’s
Focal high uptake
Toxic multinodular goitre
Adenomas
Cold (abnormally low)
Thyroid cancer
