Term
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Definition
Develops from foramen cecum
Migrates downward to adult location
May migrate substernal
May not migrate as far as normal
Right and left lobes connected by an isthmus
When stress abates, involution occurs
Follicle cell height decreases
Colloid accumulates
Goitrogens
Suppress synthesis of T 3 and T4
TSH increases
Hyperplastic enlargement |
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Term
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Definition
Produces T 3 and T4 which are mostly bound to TBG when released into the blood.
Free T 3 and T4 interact with nuclear receptors to regulate the metabolic state of cells.
During stress
Thyroid enlarges
Transient hyperplasia occurs
Follicular cells become columnar |
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Term
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Definition
Many drugs and diseases alter thyroid transport protein concentrations
Assays need to distinguish between increased and decreased total (mostly bound, inactive) and free T4 and T3
Excess or deficiency of free T4 and free T3 determine
Hyperthyroidism
Hypothyroidism
T4 levels are routinely measured
T3 levels do not provide as good a general test of thyroid status
levels fluctuate rapidly in response to
stress
other non-thyroidal factors |
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Term
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Definition
Hypermetabolic state caused by increased free T 4 and / or T3
Overproduction by the thyroid (Graves’ disease)
Overproduction outside the thyroid - excess peripheral conversion of T 4 to T3
Loss of storage function - leakage of hormone from a non-hyperactive gland
Free T4 increased
Free T3 increased
TSH decreased
except when produced by a pituitary adenoma
“T3 toxicosis” is an exception
Selective increase in Free T3
Free T4 normal |
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Term
| Causes of hyperthyroidism |
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Definition
Graves’ Disease - most common cause
diffuse toxic goiter
85% of thyrotoxicosis cases
Functioning thyroid nodule
nodular goiter; neoplasm, usually adenoma
Thyroiditis
Administration of thyroid hormone
Chorionic thyroid stimulators (hCG)
Pituitary adenoma (rare) |
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Term
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Definition
Most common cause of hyperthyroidism
Affects 1.5 to 2% of women in the U.S.
F:M = 7:1
HLA-B8 and DR3 association in caucasians
Anti-TSH-receptor IgG antibodies mimic the action of TSH
Thyroid-stimulating IG (TSI)
Thyrotropin-binding inhibitor immunoglobulin (TBII)
Unknown what triggers autoimmune RXN
Ophthalmopathy; muscles, soft tissues
Many T-lymphocytes
Increased glycosaminoglycans |
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Term
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Definition
This test is occasionally done to confirm TSH suppression in hyperthyroid patients.
IV TRH; TSH at 0, 20-30, 60 minutes
Normal - two-fold increase
Hyperthyroid - low baseline TSH and lack of response to TRH
Hypothyroid - exaggerated increase in primary hypothyroidism |
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Term
| Thyroid Peroxidase Antibodies |
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Definition
Positive in majority of patients with autoimmune thyroid disease
Nearly all adults with Hashimoto’s thyroiditis
85% Graves’ disease
Useful test to confirm the diagnosis of Hashimoto’s thyroiditis in individuals with goitrous hypothyroidism |
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Term
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Definition
The thyroid may become enlarged and painful.
Secondary scarring may simulate malignancy via adherence to adjacent structures.
The three most common varieties are: Hashimoto’s thyroiditis Subacute granulomatous thyroiditis Subacute lymphocytic thyroiditis |
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Term
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Definition
Most common cause of non-iodine deficient goitrous hypothyroidism
Causes most non-endemic goiters in children
F:M = 10 to 20:1
Incidence increases with age; most 45 to 65
Autoimmune with antibodies to
Thyroid peroxidases
Thyroglobulin
Others (TSH receptor-blocking antibody)
Other autoimmune diseases are often present (SLE, RA, PA, Sjögren's, Graves’)
Morphology (goitrous variant)
Extensive replacement of thyroid by lymphocytes, plasma cells, immunoblasts, macrophages
Germinal centers usually present
Hürthle cells (degenerated follicle lining cells)
Clinical Course
Middle-aged female with enlarged thyroid is typical
Atrophic (fibrosing) variant may not produce enlargement
Prognosis excellent with hormone replacement
Small increased risk of B-cell lymphoma, possibly carcinoma |
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Term
| De Quervain's Thyroiditis |
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Definition
Subacute
Sudden onset, often following upper respiratory tract infection
Painful enlargement of the thyroid persists for weeks to months
Granulomatous - inflammation liberates colloid which elicits foreign body reaction
Probable viral cause, tendency to recur |
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Term
| Subacute Lymphocytic Thyroiditis |
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Definition
Uncommon cause of goitrous hyperthyroidism
Painless
Differs from Hashimoto’s:
Inflammation all lymphocytes
No germinal centers
No Hürthle cell change
May be antithyroid antibodies in low titers
Any age; F > M
Most common in post-partum women
HLA-DR3, DR-5; genetic susceptibility? |
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Term
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Definition
Primary - Thyroid failure
Diagnosis - significantly increased TSH
Patients may have normal T4 and Free T4
Isolated increase in TSH
Exaggerated response following IV TRH
Central - Pituitary or Hypothalamic failure
TSH levels inappropriately normal |
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Term
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Definition
Results from hypothyroidism during development and infancy
Seldom obvious at birth
Becomes evident within weeks to months
Severe physical & mental retardation
Endemic - lack of dietary iodine
Sporadic
Anatomic - thyroid aplastic or destroyed in utero
Biochemical - thyroid present and enlarged, hormone production deficient |
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Term
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Definition
Term applied to hypothyroidism in adult or older child
Insidious onset, may go unrecognized for years
Anatomically there is an accumulation of hydrophilic mucopolysaccharide in connective tissues throughout the body.
There is doughy thickening of the skin which appears edematous and resists pitting.
Fatigue, lethargy, cold intolerance
General listlessness
Speech & intellectual functions slowed
Periorbital edema
Thickened, dry, coarse skin
Thickened facial features, tongue
Peripheral edema
Extreme physical & mental torpor
Heart flabby, dilated, advanced cases |
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Term
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Definition
Thyroid cancer is uncommon in U.S.
2/3 in females
< 1% of cancer deaths in U.S.
Almost all are carcinomas
sarcomas,lymphomas are rare
Most are well-differentiated and have estrogen receptors |
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Term
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Definition
Adenomas
Derived from follicular epithelium
Encapsulated
Microscopic: small or large follicles, cords, trabeculae, fetal-like, &ct.
If it is papillary, it is carcinoma Others Dermoid cysts, teratomas, lipomas, hemangiomas |
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Term
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Definition
Papillary or follicular growth pattern histologically
Diagnosis depends on cytologic features
Pale nuclei due to finely dispersed chromatin
Nuclear grooves
Intranuclear inclusions
Prognosis is good |
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Term
| Medullary Thyroid Carcinoma |
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Definition
Neuroendocrine
Parafollicular C-cell origin
Most secrete calcitonin
Many have distinctive amyloid stroma
20% in MEN and other familial patterns
80% sporadic
Gross
Discrete tumor in one lobe (sporadic)
Numerous nodules in both lobes (familial)
50% survival for 10 yrs |
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Term
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Definition
Rare
Elderly
Very aggressive cancer
Rapidly growing
Poor survival - usually fatal within one year
Endemic goiter regions
Spindle cell and Giant cell subtypes |
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