Investigations/Hypo/Hyper Flashcards
(23 cards)
A thyroid uptake scan is useful for
the differential diagnosis of hyperthyroidism by determining whether increased radiotracer uptake occurs diffusely throughout the gland as in the case of Graves disease or in more discrete “hot” nodules in cases of solitary toxic adenoma or toxic multinodular goiter (TMG).
CT
helpful particularly for two scenarios: substernal (intrathoracic) goiter and advanced thyroid cancer
cross-sectional imaging more readily detects vascular anomalies such as the lusoria artery
superiority over MRI in the detection of cervical lymph node metastases
For evaluation of substernal goiter, a noncontrast CT or MRI is sufficient.
On the other hand, IV contrast is indicated for clinical suspicion of advanced thyroid cancer such as locally advanced tumors or those with multiple and/or bulky lymph node metastases.
The role of [ 18 F]-fluorodeoxyglucose PET
is limited to selected cases of higher-risk thyroid cancers, such as for surveillance and staging for RAI-refractory DTC.
chronic lymphocytic thyroiditis»_space; Hashimoto thyroiditis
females
strong hereditary component
infiltration of lymphocytes into the thyroid follicles and eventually results in fibrosis,
TPOAb and TgAb
Sonographic characteristics
coarse, heterogeneous, and hypoechoic parenchymal echotexture with increased vascularity, often with the presence of fine echogenic septae producing a pseudonodular appearance that can sometimes be confused with discrete thyroid nodules
Cont Hashimoto thyroiditis
associated with an increased risk of papillary thyroid cancer (PTC)
Primary thyroid lymphoma, associated with Hashimoto thyroiditis and can often be difficult to distinguish based on cytology due to similarities around having large numbers of lymphoid cells
Cytologic features of hashimoto
moderately cellular specimen with aggregates of follicular cells with oncocytic/Hürthle cell changes, minimal colloid, and infiltration of mature lymphocytes. Giant cells, plasma cells
second most common type of autoimmune thyroiditis
postpartum thyroiditis
within the first 2 to 12 months of the postpartum period
1) hypothyroidism may be preceded by a short thyrotoxic state
2) it is often associated with the presence of circulating TPOAb
3) postpartum thyroiditis is associated with a ten-fold risk of ultimately developing Hashimoto thyroiditis
Subacute Thyroiditis/ de Quervain disease
female preponderance
fourth decade of life.
after a viral prodrome such as an upper respiratory infection.
The hallmark of the clinical presentation : pain and swelling
elevated erythrocyte sedimentation rate, which is diagnostic.
can be associated with transient hyperthyroidism followed by hypothyroidism.
Cytopathologic include the presence of multinucleated giant cell granulomas.
time course of de Quervain thyroiditis is typically 2 to 5 months, no pecific Tx
NSAIDS for pain, Steroids if sever
Riedel Thyroiditis
diffuse destruction and fibrosis of the thyroid.
No malignancy Risk
extends into surrounding structures, including the aerodigestive tract and RLN
biochemical markers of hypothyroidism
Ultrasound :
diffusely hypoechoic gland with ill-defined borders.
FNA cytology reveals dense fibrotic changes but cannot be reliably distinguished from fibrotic changes often associated with anaplastic thyroid cancer (ATC).
Tx: corticosteroids and tamoxifen.
Thyroid hormone supplementation/replacement
Surgical resection is often indicated to rule out malignancy such as ATC or primary thyroid lymphoma or to treat aerodigestive tract obstruction
simple wedge resection of the isthmus being the most common surgical therapy for relief of tracheal compression.
Acute Suppurative Thyroiditis
acute pyogenic infection
The most common underlying cause is infection of a congenital pyriform sinus fistula
swelling at the thyroid gland (typically left-sided)
and cervical lymphadenopathy.
The most common organisms include the Staphylococcus and Streptococcus
lead to thyroid abscess
retropharyngeal abscess, tracheal obstruction, mediastinitis, and jugular venous thrombosis
Take FNA and C/S
CBC, TFT not helpful
Tx : Abx and Drianage
Iatrogenic Hypothyroidism
pharmacotherapy is the primary cause of iatrogenic hypothyroidism
most common medications associated with hypothyroidism include
RAI (131I)
antithyroid thionamides (such as methimazole and propylthiouracil [PTU])
amiodarone
lithium
immune modulators
kinase inhibitors.
etiology of drug-induced hypothyroidism
- RAI therapy, the often-expected hypothyroidism is due to direct destruction of the thyroid follicular
- methimazole and PTU directly inhibit T4 and T3 synthesis (as well as block peripheral conversion of T4 to T3 in the case of PTU)
- amiodarone can lead to both hypothyroidism and hyperthyroidism
» inability to escape from the Wolff-Chaikoff effect from the drug’s high iodine content
» inhibition of deiodinase activity
» inhibition of thyroid hormone entry into the periphery, and direct cytotoxic thyroiditis - Lithium may act by directly inhibiting the cAMP-dependent pathway
- Tyrosine kinase inhibitors such as sunitinib and vandetanib cause hypothyroidism in different ways
» direct destructive autoimmune thyroiditis
reduction in vascular endothelial growth factor (VEGF)
reduction of thyroid iodine uptake
Graves Disease 1
- activation of the TSH receptor by TRAb,
- most common cause of hyperthyroidism in the United States
- female predominance
- during younger adult life
- 30 % autoimmune reactions at the orbital and periorbital soft tissues
- can lead to vision loss from corneal lesions or optic nerve compression
- Sonographic features diffusely hypervascular gland, with heterogeneous echogenicity
- 99m technetium pertechnetate or 123I differentiate TSI-negative Graves disease from toxic nodular disease based on diffuse versus nodular uptake pattern.
- CT of the head may be useful for the evaluation of orbitopathy.
Graves Disease 2
- management options for Graves hyperthyroidism:
antithyroid medications, RAI ablation, and thyroidectomy. - RAI is the most common employed treatment option
thyroidectomy is the preferred modality in the following situations:
-presence of severe eye disease
-failure or contraindications to other treatment options,
-need or desire for rapid reversal of hyperthyroidism,
-presence of concomitant suspicious thyroid nodules,
-large goiters with locally compressive symptoms
-and pregnancy or postpartum/breastfeeding states
Pre Op for Graves
> > rendered euthyroid prior to thyroidectomy
methimazole
PTU was found to be associated with liver failure resulting in the need for transplantation.
> > Beta blockers
Lugol solution for 7 to 10 days prior to surgery;
decreasing thyroid blood flow and vascularity
via the Wolff-Chaikoff effect
> > optimization of calcium and vitamin D status
calcitriol, has been shown to decrease the postoperative risk of transient hypocalcemia.
Thyroid Storm
- severe, uncontrolled hyperthyroidism
- Tx : beta blockade, antithyroid medications, potassium iodide, corticosteroids, mechanical cooling therapies, and intensive supportive care
Toxic Multinodular Goiter 1
- one or more autonomously functioning nodules leading to a state of hyperthyroidism
- TSH Receptor Gene Mutation
- AKA Plummer disease
- second most common cause of hyperthyroidism
- These “warm” or “hot” nodules are rarely malignant and typically do not require biopsy
- FNA to NON Functional Nodes
- TRAb is necessary to identify coexisting autoimmune thyroiditis and rule out Graves disease
- Nuclear scintigraphy is a first-line imaging study
Toxic Multinodular Goiter 2
- three management options —antithyroid medication, RAI, and thyroidectomy
- antithyroid medication is generally not advocated as a long-term management strategy
- autonomous nodules do not undergo remission with medical therapy
- , RAI with 131I is the most common definitive treatment for TMG in the United States
- however, the dose of radiation is typically higher
- methimazole with or without beta blockade;
- SSKI and Lugol solutions are not indicated for TMG
» They induce hyperthyroidism from the Jod-Basedow phenomenon
Solitary Toxic Adenoma
- activating mutations in the TSH receptor gene
- antithyroid medications are not effective for long-term remission
- RAI or thyroidectomy is the preferred method for definitive treatment.
- Thyroidectomy is typically limited to unilateral lobectomy
Amiodarone-Induced Thyrotoxicosis
Type 1 AIT is caused by the Jod-Basedow phenomenon, in which the high iodine load potentiates excess thyroid hormone synthesis and release.
Type 1 AIT is more common in patients with preexisting hyperthyroid disease.
Type 2 AIT usually occurs in patients with preexisting normal thyroids and is caused by a destructive thyroiditis from direct drug toxicity on follicular cells leading to release of preformed thyroid hormone
Medical treatment of AIT typically consists of methimazole, with corticosteroids added to address the thyroiditis in type 2 AIT
Nontoxic Multinodular Goiter
the causes of the majority of sporadic multinodular goiter remain unknown.
Endemic (Diffuse) Goiter
only known cause of endemic goiter is dietary iodine deficiency
Substernal Goiter
- gland extending inferiorly through the thoracic inlet and into the mediastinum.
- The most common subtype extends into the anterior mediastinum.
- The second subtype extends posteriorly to the great vessels, trachea, and/or RLN, sometimes crossing over to the contralateral neck.
- The third and least common subtype is the isolated mediastinal goiter with no connection to the normal cervical orthotopic gland and with unique blood supply from the chest
When to think Sternotomy
- goiters extending further inferiorly than the aortic arch,
- extending posteriorly
- and/or crossing the midline from the dominant side
