Thyroid & Parathryoid Flashcards
Where is the thyroid located?
- anterior neck lateral to trachea
- inferior to thyroid cartilage
- medial to IJV and CCA
What are the parts of the thyroid?
Right and left lobes and isthmus
What anatomical variants of the thyroid gland are there?
Pyramidal lobe
What is a pyramidal lobe? How often does it occur?
A superior sliver of thyroid tissue arising from the isthmus, “3rd lobe”
Occurs in up to 30% of pop
What kind of cells compose the thyroid gland?
Follicular and parafollicular cells
What size is the normal thyroid? (Length, AP, width)
Length: adult 4-6 cm, ped 2-3 cm
AP: adult 2-3 cm, ped 1.2-1.5 cm
Width: adult 1.5-2cm, ped 1-1.5 cm
What is considered an enlarged thyroid?
Isthmus > 1 cm
AP > 2 cm
What muscles are anterior to the thyroid?
- sternohyoid
- sternothyroid
- omohyoid
What muscle is anterolateral to the thyroid?
Sternocleidomastoids
What vessels are lateral to the thyroid?
Common carotid artery and internal jugular vein
What structure is posterior to the thyroid?
Parathyroid glands
What muscle is posterolateral to the thyroid?
Longus colli
What structures are medial to the thyroid?
Trachea and esophagus
What supplies the thyroid gland?
Superior thyroid artery: branch of ECA, descends to supply superior portion of thyroid
Inferior thyroid artery: branch of thyrocervical trunk, ascends to supply inferior portion of thyroid
What drains the thyroid?
- Superior thyroid vein: drains into IJV
- Middle thyroid vein: drains into IJV
- Inferior thyroid vein: drains into left brachiocephalic vein
What 3 hormones are secreted by the thyroid gland?
- Thyroxine (T4): metabolic rate
- Triiothyronine (T3): metabolic rate
- Calcitonin: calcium metabolism
What is TSH?
Thyroid stimulating hormone: controlled by pituitary gland
Controls hormone secretion from thyroid
What is TRH?
Thyrotropin releasing hormone: controlled by hypothalamus
Regulates secretion of TSH
What do thyroid follicular cells do?
They are the only cells that absorb iodine
How are thyroid hormones produced?
Through iodine metabolism
What is the process that occurs for thyroid hormones to be secreted?
- low thyroid hormones
- drop in basal metabolic rate
- increase in thyrotropin releasing hormone
- increase in secretion of thyroid stimulating hormone
- increase in thyroid hormones
When does TSH stop being released?
When thyroid hormones return to normal and basal metabolic rate is normal
What lab values are we looking at?
- thyroxine
- triiodothyronine
- TSH
- calcitonin
What nuclear medicine tests are used for the thyroid?
Scintigraphy: iodine uptake scan and thyroid scan
What is the sonographic appearance of the normal thyroid?
- homogenous
- mid level echogenicity
- echogenic compared to surrounding musculature
- symmetric lobe size/appearance
- symmetric vascularity throughout
What indicates the need for a thyroid ultrasound?
- abnormal lab values
- weight control complications
- palpable lump
- swelling/asymmetry
- dysphagia
- family history of thyroid disease/cancer
- post thyroidectomy
How are measurements taken for the thyroid?
Length and AP in sag, width in trans
What causes hypothyroidism?
- low iodine intake
- thyroid hormone failure
- pituitary or hypothalamus disease
What are clinical symptoms of hypothyroidism?
- weight gain
- constipation
- brain fog
- cold intolerance
- increased tissue around eyes
- lethargy
- deep husky voice if untreated
What is the sonographic appearance of hypothyroidism?
- goiter in initial stages
- diffuse nodularity
- over time, thyroid will atrophy
What causes hyperthyroidism?
- abnormal hormone secretion
- localized mass causing overproduction of hormones
- Grave’s disease
What is the sonographic appearance of hyperthyroidism?
- homogenous, often heterogenous due to enlargement and nodules
- hypoechoic
What are the clinical symptoms of hyperthyroidism?
- rapid increase in metabolic rate & weight loss
- increased appetite
- nervousness
- tremors
- sweating
- palpitations
- exophthalmos
What is the most common cause of hyperthyroidism?
Grave’s disease
What is Grave’s disease also called?
Thyrotoxicosis, thyrotoxic crisis, thyroid storm
Who does Grave’s disease most commonly occur in?
Women over 30
What does Grave’s disease cause production of?
Thyroid stimulating immunoglobin
What is the sonographic appearance of Grave’s disease?
- hypoechoic
- enlarged
- homogenous, but can be heterogenous due to enlargment/nodules
- hypervascular
What are the clinical symptoms of Grave’s disease?
- goiter
- opthalmopathy
- tachycardia
- tremors
- muscle weakness
- weight loss
What causes thyroiditis?
Infection or autoimmune abnormality
What are clinical symptoms of thyroiditis?
- swelling/tenderness of thyroid
- chronic: hypothyroidism due to loss of functional tissue over time
What is De Quervain’s thyroiditis?
- AKA subacute thyroiditis
- viral inflammatory disorder
- causes focal or diffuse enlargement
How can thyroiditis be distinguised from De Quervain’s thyroiditis?
Thyroiditis causes hypervascularity and De Quervain’s appears with normal or decreased vascularity
What are the symptoms of De Quervain’s?
- fever
- neck pain
- fatigue
- tenderness
- dysphagia
What is the most common form of thyroiditis?
Hashimoto’s disease
What is Hashimoto’s disease and who does it affect?
- autoimmune disorder causing chronic inflammation of the thyroid
- affects young/middle aged women
What are the clinical symptoms of Hashimoto’s disease?
- diffuse enlargement/asymmetric
- painless/mild pain
- chronic: hypothyroidism
What is nontoxic multinodular goiter?
- AKA MNG
- diffuse thyroid enlargement not caused by neoplasm or infection
- cannot provide adequate supply of thyroid hormone due to nodules
- can be caused by iodine shortage or gland malfunction
- unknown/nonspecific reason
What are the clinical symptoms of NTMNG?
- goiter
- hypothyroidism
- difficulty breathing/swallowing due to goiter compressing trachea, esophagus, vessels
What is toxic multinodular goiter?
- hyperplasia of the thyroid, associated primarily with hyperthyroidism
What are the clinical symptoms of TMNG?
- abnormal TSH
- hyper/hypo thyroidism
- more often increased hormone levels (hyper)
What is a colloid cyst?
- benign fluid-filled sac within thyroid tissue
- dilation of follicular tissue
- commonly has central echogenic foci with “comet tail” underneath
- typically small but can grow
What are thyroid nodules?
- clusters of tissue accumulating into a “ball”
- cause variable gland enlargement
What cause thyroid nodules?
- thyroiditis (ill-defined), tissue is walled off after infection
- neoplasm (benign or malignant accumulation of tissue)
- nodular hyperplasia
- Hashimoto’s (micronodules)
What is a cystic nodule?
- less common finding
- related to degeneration of an adenoma
- adenoma can degenerate over time and be replaced with cystic fluid
- can have mixed solid and cystic components due to remaining adenoma tissue
What is a follicular neoplasm?
- benign but can be precancerous
- proliferation of functional follicular cells
What is a thyroglossal duct cyst?
- congenital anomaly
- midline and anterior to trachea
What are clinical symptoms of thyroglossal duct cyst?
- palpable, midline mass
- pain associated with hemorrhage or infection
What is a branchial cleft cyst?
- remnant of embryonic development
- seen lateral to thyroid
What are clinical symptoms of BCC?
- asymptomatic but will become palpable as it grows
What is a cystic hygroma?
- congenital lymphatic malformation
- posterolateral on neck
- fetuses can develop
What are the clinical symptoms of cystic hygroma?
- webbed neck
- palpable, soft mass
What is papillary carcinoma?
- most common thyroid cancer
- least aggressive, best prognosis
- major route of mets is via regional lymph channels (cervical lymph nodes)
What are the clinical symptoms of papillary carcinoma?
- asymptomatic
- palpable lump
What are microcalcifications AKA?
psammoma bodies
What is follicular carcinoma?
- more aggressive than papillary carcinoma
- 2nd most common
- spreads through bloodstream & metastasizes to bone, brain, lung, liver, not to cervical lymph nodes
Who is follicular carcinoma typically seen in?
Older females
What is medullary carcinoma?
- less common thyroid malignancy, 10%
- originates from parafollicular cells which secrete calcitonin
What are the clinical signs of medullary carcinoma?
- hard palpable nodule
- abnormal serum calcitonin levels
What is anaplastic carcinoma?
- rare, less than 10% of thyroid cancers
- most deadly
- affects patients over 50
What are the clinical signs of anaplastic carcinoma?
- hard, fixed mass
- rapid growth
- pain, pressure, tenderness
- locally invasive
What is the cause of death for many patients with anaplastic carcinoma?
asphyxiation due to rapid growth of mass compressing trachea
Lymphoma within the thyroid
- primarily non-Hodgkin’s lymphoma within the thyroid
- occurs mainly in older females
- 4% of thyroid cancers
What are the clinical signs of/risks for thyroid lymphoma?
- rapid growth of neck mass
- Hashimoto’s thyroiditis is a risk factor for developing lymphoma originating in the thyroid
What is primary hyperparathyroidism?
- increased function of parathyroids
- increased amounts of PTH are produced by an adenoma, carcinoma, or primary hyperplastic parathyroid gland
- 3 times more common in women, especially after menopause
What are the clinical signs of primary hyperparathyroidism?
- hypercalcemia
- hypercaluria
What is the sonographic appearance of primary hyperparathyroidism?
- enlarged, hypoechoic glands
What is secondary hyperparathyroidism?
- occurs with chronic renal failure patients
- the inability to synthesize vitamin D decreases serum calcium level
- may affect all 4 PT glands
What is the sonographic appearance of of secondary hyperparathyroidism?
- enlarged, hypoechoic glands
What is the most common cause of primary hyperparathyroidism?
Parathyroid adenoma
What is parathyroid carcinoma?
- Small percentage of patients with primary hyperparathyroidism will have PTC
- malignant neoplasm
- hard to differentiate between PTC and PT adenoma, diagnosed by surgical excision
What criteria does TIRADS grade based on?
- comp
- echo
- shape
- margins
- echo foci
- sig change in size
- change in feature
- change in ACR risk cat
What is the most common form of thyroiditis?
Hashimoto’s disease
What structure is located to the left of midline and often mistaken for a thyroid lesion?
Esophagus
Which parathyroid pathology is associated with patients who have chronic renal failure?
Secondary hyperparathyroidism
What are the parathyroid glands?
Endocrine organ posterior to thyroid gland, 2 pairs of oval glands
What is the normal size of PT glands?
5 x 3 x 1 mm
What do PT glands do?
Maintain proper levels of calcium ions in blood
What is parathormone?
Hormone produced by PT glands when calcium is low, triggers glands to produce more calcium
