Thyroid Flashcards
What is the normal range of TSH?
0.33-4.5mu/l
What is the normal range of free T4?
10.2-22.0pmol/l
What is the normal range of free T3?
3.2-6.5pmol/l
What does an elevated serum TSH but low T4 mean?
Hypothyroidism
What does an elevated serum TSH but normal T4 mean?
Treated hypothyroidism or subclinical hypothyroidism
What does an elevated serum TSH and elevated T4 mean?
TSH secreting tumour or thyroid hormone resistance
What does a decreased serum TSH but increased T4 mean?
Hyperthyroidism
What does a decreased serum TSH but normal T4 mean?
Subclinical hyperthyroidism - this may progress to primary hypothyroidism, especially if the patient is anti-TPO antibody positive
What does a decreased serum TSH and decreased T4 mean?
Central hypothyroidism (hypothalamic or pituitary disorder)
What does an increased serum TSH but decreased T4, followed by a decreased TSH and T4 mean?
Sick euthyroidism
What does a normal TSH but abnormal T4 mean?
Assay interference, changes in thyroxine binding globulin, or SE of amiodarone
Name three causes of hyperthyroidism with high uptake on a radioactive iodine uptake test
Graves disease, toxic multinodular goitre, toxic adenoma
Name two causes of hyperthyroidism with low uptake on a radioactive iodine uptake test
Subacute De Quervains thyroiditis, postpartum thyroiditis
Name two autoimmune causes of hypothyroidism
Primary atrophic hypothyroidism, Hashimotos thyroiditis
State three non-autoimmune causes of hypothyroidism
Iodine deficiency, thyroidectomy, radio-iodine, drug-induced (carbimazole, lithium, amiodarone)
What is the female to male ratio of Graves disease?
9:1
What is de Quervain’s thyroiditis?
Self-limiting post-viral goitre, painful, initially causes hyperthyroidism then hypothyroidism
Which group are most commonly affected by Hashimotos thyroiditis?
Elderly females
Name the two autoantibodies which may be found in Hashimotos thyroiditis
anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-TG)
How is hyperthyroidism treated?
Carbimazole as an anti-thyroid
Beta blockers for symptom relief, topical steroids for dermopathy
If carbimazole fails, radio-iodine
What are the side effects of carbimazole?
Rashes (common), agranulocytosis (rare)
State the six indications for hemi or total thyroidectomy
Hyperthyroidism in a woman intending to become pregnant in the next 6 months, oesophageal or tracheal compression by thyroid goitre, cosmetic removal of thyroid goitre, suspected thyroid cancer, co-existing hyperparathyroidism, hyperthyroidism refractory to medical therapy
Describe the presentation of a thyroid storm
Shock, pyrexia, confusion, vomiting
How is a thyroid storm managed?
ITU admission, cooling, high dose anti-thyroid medications, corticosteroids, circulatory and respiratory support
Name the five types of thyroid neoplasia
Papillary, follicular, medullary, lymphoma, anaplastic
Describe the appearance of papillary thyroid cancer on histology
May see psammoma bodies
What is the most common age range for developing papillary thyroid cancer?
30-40
How is papillary thyroid cancer treated?
Surgery, radio-iodine, thyroxine to decrease TSH
Which type of thyroid cancer is linked to MEN2?
Medullary thyroid cancer
What is the main risk factor for thyroid lymphomas?
Chronic Hashimotos thyroiditis
Where does medullary thyroid cancer originate?
Parafollicular C cells which produce calcitonin
Which endocrine cancers does MEN1 predispose to?
Pituitary, pancreatic (e.g. insulinoma), parathyroid
Which endocrine cancers does MEN2a predispose to?
Parathyroid, phaeochromocytoma, medullary thyroid
Which endocrine cancers does MEN2b predispose to?
Phaeochromocytoma, medullary thyroid, mucocutaneous neuromas
