Chemical Pathology - Thyroid Flashcards
(41 cards)
What are some causes of a raised TSH and low T4?
Hypothyroidism
- Atrophic
- Hashimoto’s
- Subacute (De Quervain’s)
- Postpartum
- Riedel thyroiditis
What are some causes of a raised TSH and normal T4?
- Treated hypothyroidism
- Subclinical hypothyroidism
What are some causes of a raised TSH and raised T4?
- TSH secreting tumour
- Thyroid hormone resistance
What are some causes of a low TSH and raised T4 or T3?
Hyperthyroidism
- Grave’s disease
- Toxic multinodular goitre (Plummer’s)
- Toxic adenoma
- Drugs (thyroxine, amiodarone)
- Ectopic (Trophoblastic tumour, struma ovarii)
What is the cause of a low TSH and normal T3 or T4?
Subclinical hyperthyroidism
- Might progress to primary hypothyroidism (particularly if pt is anti-TPO antibody +ve)
What are some causes of a low TSH and low T4?
Secondary hypothyroidism
- Hypothalamic/pituitary disorder
What is the cause of a raised then low TSH, and low T3 + T4 and why?
Sick euthyroid (with any severe illness)
- Body tries to shit down metabolism as thyroid gland has reduced output
What are some causes to a normal TSH and abnormal T4?
- Assay interference
- Changes in TBG
- Amiodarone
What is the treatment of hypothyroidism?
Thyroid replacement therapy
What is the medical treatment for hyperthyroidism?
- Sx relief: β blockers, topical steroids (dermopathy), eye drops for Sx eye disease with Graves
- Antithyroid medications (Carbimazole)
What are the two approaches to giving antithyroid medication in hyperthyroidism and some side effects?
- Titration to normal T3
- Block + replace (cause hypothyroidism then give levothyroxine) - uncommon at high risk of SEs
SEs:
- Agranulocytosis
- Rashes (common)
When is radio-iodine used in the treatment of hyperthyroidism and what is its main risk?
- After medical therapy has failed
- CI: Pregnancy + lactating women
Risk:
- Permanent hypothyroidism
What are the seven indications for a surgical hemi/total thyroidectomy in a patient with hyperthyroidism?
- Women intending to become pregnant in next 6/12
- Local compression secondary to thyroid goitre
- Cosmetic
- Suspected cancer
- Co-existing hyperparathyroidism
- Refractory to medical therapy
What is a thyroid storm and how is it treated?
- Acute state that presents as shock with pyrexia, confusion + vomiting
Tx:
- HDU/ITU support
- Cooling
- High-dose anti-thyroid medications
- Corticosteroids
- Circulatory + respiratory support
Which enzyme is used to convert T4 to T3?
Deiodinase enzyme
What are the roles of T3?
- Acts as intramuscular receptor
- Regulates basal metabolite rate
- Potentiates response to catecholamines
How is thyroxine produced?
- Thyroglobulin is produced in the follicular glands
- Thyroglobulin is moved into the colloird where it is oxidised, iodinated + molecules are couples (T4)
- T4 moved back to the follicular cell and then secreted in the blood stream
What enzyme is used in the oxidation process of thyroglobulin?
Thyroperoxidase enzyme
What are three causes of high uptake hyperthyroidism?
- Graves Disease
- Toxic multinodular goitre
- Toxic adenoma
What are three causes of low uptake hyperthyroidism?
- Subacute De Quervains Thyroiditis
- Portpartum thyroiditis (Like De Quervain’s but post-partum)
- Ectopic
What are two causes of autoimmune hypothyroidism?
- Primary Atrophic HypoT (Commonest cause in UK)
- Hashimoto’s Thyroiditis
What are other causes of hypothyroidism?
- Iodine deficiency (Most common worldwide)
- Post-thyroidectomy/radioiodine
- Drug induced
- Riedel’s thyroiditis
What are some features of Graves Disease?
- 40-60% of all hyperthyroidisms
- F > M (9:1)
Sx:
- Painless goitre
- Anti-TSH receptor Abs
- High diffuse uptake (isotope scan)
What are some features of a toxic multinodular goitre (Plummer’s)?
- 30-50% of all hyperthyroidisms
Sx:
- Painless
- High uptake hot nodules (isotope scan)
- Enlarged follicular cells distended with colloid + flattened epithelium
