Thyroid Flashcards
What are the two main cell types of the thyroid gland?
Follicular and parafollicular
What is the role of parafollicular cells?
Secretes calcitonin
How do thyroid hormones affect protein synthesis?
Stimulation of protein synthesis
How do thyroid hormones affect carbohydrates and lipids?
Increases carbohydrate and lipid catabolism
How do thyroid hormones affect the CNS?
They play a critical role in the development of the brain in fetuses and neonates
Differentiate hyperthyroidism from thyrotoxicosis
Thyrotoxicosis- elevated T4/T3 in the body (endogenous or exogenous, or struma ovarii)
Hyperthyroidism- hyperfunctioning of the thyroid gland
Describe the CNS/neuromuscular symptoms of hyperthyroidism
nervousness, emotional lability, insomnia, muscle weakness, fine tremor of the hands
What are the ocular symptoms of hyperthyroidism?
wide staring gaze and lid lag
What is the single more sensitive screening test for hyperthyroidism?
TSH measurement
Low in hyperthyroidism
Following a radioactive iodine uptake administration, what would the uptake pattern be in Graves disease, toxic adenoma, and thyroiditis?
Graves- diffuse uptake
Toxic adenoma- localized
Thyroiditis- reduced uptake
What is the most common cause of hypothyroidism in developing countries? In developed countries?
Developing countries: iodine deficiency
Developed countries: Hashimoto’s thyroiditis
What is the secondary cause of hypothyroidism?
Pituitary failure
What is hypothyroidism of children called? Adults?
Infants/early childhood- cretinism
Adults- myxedema
What are the sequelae of cretinism?
Depends on when the iodine deficiency occurred- if mom is also iodine deficient, it is worse
Mental retardation, short stature, coarse facial features
What are the characteristics of myxedema?
Gradual slowing of mental/physical function
Fatigue, lethargy, apathy, slowed speech…
What is the most sensitive screening test for hypothyroidism?
TSH levels (they will be increased)
Name two types of thyroiditis with pain
Infectious- usually bacterial, you don’t intervene
Subacute granulomatous De Quervain’s thyroiditis
List three types of painless thyroiditis
Subacute lymphocytic thyroiditis
Reidel’s thyroiditis
Hashimoto’s thyroiditis
What is the cause of Hashimoto’s thyroiditis?
Autoimmune destruction of thyroid gland –> failure and hypothyroidism
What are the three immunologic attacks against the thyroid?
CD8+ cytotoxic T cells
IFN-gamma/pro-inflammatory cytokine destruction
Anti-thyroid antibodies
What are the three autoimmune antibodies seen in Hashimotos?
TPO
TSH receptor
Iodine receptor
What is the characteristic cell seen in Hashimoto’s thyroiditis?
Hurthle cells/ oncocytes - loaded with mitochondria and therefore appear granular/very pink
People with Hashimoto’s are at increased risk of developing what neoplasm?
Non-Hodgkins B cell lymphoma
What is the etiology of De Quervain’s thyroiditis?
Viral or Post-viral inflammatory response-
Either viral antigens or infection induced T-cell activation leads to destruction of thyroid cells
What is the prognosis of De Quervain’s thyroiditis?
Self-limited
Is De Quervain’s thyroiditis painful or painless?
Painful
What is the clinical course of De Quervain’s thyroiditis?
History of upper respiratory infection
Transient hyperthyroidism diminishing in 2-6 weeks
Recovery to normal function in 6-8 weeks
What are the symptoms of Riedel’s thyroiditis?
Extensive fibrosis involving thyroid and contiguous neck structures (goes OUTSIDE the thyroid and squeezes those structures)
Hard and fixed masses mimic cancer
What is the most common cause of endogenous hyperthyroidism?
Graves disease
What is the triad of findings associated with Graves?
- Diffuse hyperfunctional enlargement of the thyroid
- Infiltrative ophthalmopathy –> exophthalmos
- Infiltrative dermopathy - pretibial myxedema
What is the most common autoantibody seen in Graves disease?
Thyroid stimulating immunoglobulin (TSI)
-Bind the TSH receptor and mimics its action
What differentiates the histology of papillary carcinoma of the thyroid from graves?
Graves: papillary structures with NO fibrovascular core, pale colloid with SCALLOPED margins
What is a toxic vs nontoxic goiter?
Toxic: hyperfunctioning
Non-toxic: not hyperfunctioning
What is the progression of a diffuse goiter?
They all become multinodular goiters
Are the multinodular goiter thyroids usually hypothyroid, euthyroid or hyperthyroid
Euthyroid
What is Plummer’s Syndrome?
Toxic multinodular goiter due to development of an autonomous nodule
What is the most common thyroid cancer?
Papillary thyroid carcinoma
Are nodules in young patients more likely to be benign or malignant?
Malignant
What is the only benign tumor of the thyroid?
Follicular Adenoma
What are two genes seen in both follicular adenomas and follicular carcinomas?
RAS and PAX-PPARgamma fusion gene
How do we differentiate follicular adenomas from follicular adenocarcinomas?
Follicular adenomas are encompassed by a well-defined capsule (no infiltration)
What is the treatment for a follicular adenoma?
Lobectomy
These have an excellent prognosis- no recurrence
What is medullary carcinoma of the thyroid?
Neuroendocrine carcinoma of the parafollicular (C) cells
What are the histologic features of papillary carcinoma of the thyroid?
Branching papillae with a fibrovascular core lined with multiple layers of cuboidal to columnar epithelium
+ Orphan annie-eyed nuclei and psammoma bodies
Which variant of papillary carcinoma has a poor prognosis?
Tall cell variant
Papillary carcinomas with which genetic marker correlates to a worse prognosis?
BRAF
What is the most common genetic rearrangement seen in papillary thyroid canceR?
RET/PTC
Follicular carcinoma of the thyroid must be separated into what type subsets, as their prognosis is very different.
Minimally invasive- great prognosis
Widely invasive- bad prognosis
Which two hormones may be secreted in medullary carcinoma of the thyroid?
ACTH or calcitonin
Medullary carcinoma of the thyroid is associated with which MEN syndrome?
MEN2A or MEN2B
Amyloid deposition is seen in which thyroid carcinoma?
Medullary carcinoma
Which thyroid cancer has the worst prognosis?
Anaplastic carcinoma- 100% death within a year
What is a thyroglossal duct cyst and what’s the problem with it?
Incomplete atrophy of the thyroglossal duct cyst- presents at any age as a midline cyst or anterior mass
Risk of infection/abscess
