176b/177b/178b - Thyroid Physio, Path, Pathopys, Nodules, Cancer Flashcards
What are the imaging modalities of choice for evaluating thyroid structure?
Ultrasound = first line
CT if there is intrathoracic extension of large goiters
Use iodine isotopes for thyroid function
Which thyroid neoplasm is derived from C-cells?
Medullary carcinoma of the thyroid
Which type of thyroid cancer is associated with a history of radiation exposure?
Papillary carcinoma of the thyroid
Which thyroid neoplasm is most likely to have a hereditary component?
Medullary thyroid carcinoma
- Association with MEN-2
- Mutation in RET oncogene
What is the most common cause of thyroid disease worldwide?
Iodine deficiency
A patient presents with bilateral pheochromocytoma
What organ will you check next to evaluate for neoplasm?
Thyroid
- Bilateral pheo = high suspicion for MEN-2
- MEN-2A and MEN-2B both have increased risk of medullary thyroid carcinoma in addition to pheochromocytoma
- In addition:*
- MEN-2A: look for parathyroid hyperplasia*
MEN-2B: look for marfinoid appearance, ganglioneuroma
What is the most common congenital thyroid nodule?
Thyroglossal duct cyst
How does biotin supplementation affect thyroid lab values?
(TSH, T3, T4)
Why?
- Falsely low TSH
- Falsely high T4, T3
Will lead to false diagnosis of Graves’ disease!
Biotin cleaves the assay antibody (something like this)
What is organification? (in the context of TH synthesis)
What enzyme is responsible?
Organification via TPO
- Oxidation of I- to I2
- Iodination: Attach I2 to tyrosine residues on thyroglobulin
Result = Thyroglobulin with MIT and DIT
Will be coupled by TPO as well: Combine MIT and DIT
Describe the histologic features of non-invasive follicular thyroid neoplasm (NIFTP)
What is the treatment?
-
Nuclear features of papillary thyroid carcinoma
- Nuclear grooves
- Psamoma bodies
- Orphan Annie eye inclusions
-
Well encapsulated like follicular adenoma
- Well-encapsulated (uniform, continuous, fibrous capsule)
- Tumors are well-behavied
- Act like follicular adenomas
- Tx = lobecctomy
Which 3 proteins bind thyroid hormone in the blood?
- Thyroid binding globulin (TBG)
- Transthyretin
- Albumin
Affinity: TBG > Transthyretin > Albumin
Note: only very small percentages of T4 and T3 are unbound
Describe the 24h iodine uptake pattern that is pathognomonic for Graves’ disease
Diffuse, homogenous uptake
What is the role of molecular testing in the evaluation of thyroid nodules?
Test intermediate-suspicion nodules for characteristic mutations
Most useful as rule-out tests for specific pathologies
Where in the body is the thyroid hormone receptor alpha (TR-alpha) found?
What about thyroid TR-beta?
- TR-alpha
- Brain
- Skeletal tissues
- Intestines
- Heart
- TR-beta
- Liver
- Heart
Describe the findings associated with Grave’s Disease
- Gross:
- Histology:
- Gross:
- Diffuse, symmetric enlargement
- Histology:
- Papillary hyperplasia
- Tall follicular cells
What neoplasms are associated with MEN-2? (both 2A and 2B)
Which neoplasms are specific to 2A and 2B respectively?
- All MEN-2
- Medullary thyroic carcinoma
- Pheochromocytoma (medulla of adrenal gland)
- MEN-2A
- Parathyroid hyperplasia
- MEN-2B
- Marfanoid appearance
- Mucosal neuroma/ganglioneuroma
What is the histological hallmark of thyroid papillary caricinoma?
Atypical nuclear morphology
- Nuclear grooves
- Orphan Annie eye inclusions
- Hypochromasia
- Psamoma bodies
Describe the thyroid findings of Hashimoto’s thyroiditis
- Gross:
- Histology:
- Cytology:
- Gross:
- Diffusely enlarged
- Histology:
- Lymphocytes and plasma celsl infitrate parenchyma
- Atrophic follicles
- Cytology:
- Hurthle cells + heterogeneous lymphocytes
What is the classic histological finding of a follicular adenoma of the thyroid?
Normal-looking thyroid cells surrounded by a continous fibrous capsule
Note: FNA cannot distinguish between adenoma and carcinoma, but histologically, the carcinoma capsule will invade
What is the first line medication for anti-thyroid drug therapy?
Are there exceptions?
Methimazole
- Use acutely to cool the pt down prior to radioiodine or surgery
- Use long term for 12-18 months, then stop to assess remission
Exception = 1st trimester of pregnancy; use propylthiouracil (PTU) instead
List 3 substances that negatively regulate TRH secretion from the hypothalamus
Somatostatin
Dopamine
T3 (negative feedback)
What supplement may interfere with TSH, T3, T4 assays?
Biotin!
Will cause falsely low TSH, falsely high T3, T4
What etiology of hyperthyroidism will have bilateral increased iodine uptake?
Graves’ disease
What percentage of medullary thyroid carcinomas are hereditary?
What gene is likely mutated?
Which syndrome is associated?
20-25% are hereditary
RET proto-oncogene
- MEN-2 (2A or 2B)
- Association with mutations in
- Also can just be familial tumors