Chemical Pathology - Thyroid Flashcards
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
What are some features of a toxic adenoma?
- 5% of all hyperthyroidisms
- Hot nodule (isotope scan) - one area of uptake
- Solitary
What are some features of Subacute De Quervains Thyroiditis?
- Post-viral inflammation of the thyroid gland
- Self-limiting
Sx:
- Painful Goitre
- Initially hyperthyroid then hypothyroid
What are some ectopic causes of hyperthyroidism?
- Trophoblastic tumour
- Struma ovarii (excessive hCG)
What are some features of primary atrophic hypoT?
- Diffuse lymphocytic infiltration causing atrophy
Sx:
- No goitre
- Small thyroid
- No known antibodies
A/w:
- pernicious anaemia
- Vitiligo
- Endocrinopathies
What are some features of Hashimoto’s thyroiditis?
- Plasma cell infiltration
- Elderly females
- Autoimmune
Sx:
- Goitre
- Painless
- ?Initial Hashitoxicosis
- Anti-TPO + Anti-TTG
- HURTHLE CELLS
What drugs can induce hypothyroidism?
- Antithyroid drugs
- Lithium
- Amiodarone
What are some features of Riedel’s Thyroiditis?
- Dense fibrosis replacing normal parenchyma
- Painless
STONY HARD
What demographic are thyroid tumours most commonly seen in?
- Caucasian
- Middle-aged
- Women
What indicates a high risk of neoplasm in thyroid tumours?
- Solitary
- Solid
- Young
- Male
- Cold nodules
What are the five types of thyroid tumours, their prevalence, prognosis + epidemiology?
Papillary:
- 75-85%
- 20-40yrs, Female
- A/w irradiation
- V. good prognosis
Follicular:
- 10-20%
- 40-60yrs
- Good prognosis
Medullary:
- 5%
- 50-60yrs
- 80% sporadic, 20% famililal MEN2
Anaplastic:
- Rare
- Elderly
- Poor prognosis (most die <1yr)
Lymphoma:
- Diffuse large B-cell lymphoma
- Good prognosis
What are some features of Papillary Thyroid Tumours, it’s tumour marker, spread, histology + management?
- Painless cervial lymphadenopathy
- No clinical abnormalities of thyroid
- Non-encapsulated
Tumour Marker = THYROGLOBULIN
Spread = LNs + Lung
Histology:
- PSAMMOMA BODIES (foci of calcification)
- Empty-appearing nuclei with central clearning (ORPHAN ANNIE EYES)
Mx:
- Surgery +/- Radioiodine
- Thyroxine
What are some features of Follicular Thyroid Tumours, it’s tumour marker, spread, histology + management?
- Well-differentiated, encapsulated
Tumour Marker = THYROGLOBULIN
Spread = BLOOD (spreads early) then to lungs, bone, liver, breast, adrenals
Histology:
- Fairly uniform cells forming small follicles
- Reminiscent of normal thyroid
What are some features of Medullary Thyroid Tumours, it’s tumour markers, histology + management?
- Neuroendocrine neoplasm derived from PARAFOLLICULAR C CELLS secreting CALCITONIN
Tumour marker = CEA + Calcitonin
Histology:
- Sheets of dark cells, amyloid deposition within tumour (calcitonin broken down to amyloid)
Mx:
- Screen for phaeochromocytoma pre-op
- Surgery
- Node clearance
What are some features of Anaplastic Thyroid Tumours, its spread and histology?
- Early + wide metastases common
- Undifferentiated
Spread = Very aggressive (local, LNs, blood)
Histology:
- Undifferentiated follicular, large pleomorphic giant cells
- SPINDLE CELLS with sarcomatous appearance
Usually non-operable due to rapid growth
What are some features of Diffuse Large B-cell lymphoma causing a thyroid tumour, its tumour marker and RFs?
MALToma
Tumour Marker = CD20
RFs:
- Chronic Hashimoto’s (lymphocyte proliferation)
What is the basic management for a thyrotoxicosis crisis?
- Β blocker
- Steroid
- Thioamide
What are the three different types of Multiple Endocrine Neoplasia and their differences?
MEN1 (3Ps):
- Pituitary
- Pancreatic (e.g. insulinoma)
- Parathyroid (hyperparathyroidism)
MEN 2a (2Ps, 1M):
- Parathyroid
- Phaeochromocytoma
- Medullary Thyroid
Men 2b (1P, 2Ms):
- Phaeochromocytoma
- Medullary thyroid
- Mucocutaneous neuromas (+Marfanoid)
