Thyroid Test

what is the first endocrine gland to develop in the human embryo?

the thyroid gland

what does the thyroid develop from?

the floor of the primitive pharynx/base of the tongue, then it migrates inferiorly

where is the thyroid gland located?

on the anterior, inferior neck on either side of the trachea

what does the thyroid maintain?

metabolism, growth, and development

what is the thyroid regulated by?

the pituitary gland and hypothalamus

what sits just superior to the thyroid on the anterior neck?

the thyroid cartilage (adam’s apple)

what connects the right and left lobes of the thyroid?

a central bridge of tissue called the isthmus

what is the normal LONG measurement of the thyroid?

4-6cm

what is the normal AP measurement of the thyroid?

1\.5-3cm

what is the normal TRV measurement of the thyroid?

1-2cm

what is the normal measurement of the isthmus?

0\.4-0.6cm

AKA false thyroid capsule-contains more than just the thyroid itself and assists in forming the carotid sheath

pre-tracheal fascia

adheres directly to the surface of the thyroid tissue itself

true thyroid capsule

what are the two types of tissue that the thyroid is made of?

follicular cells and c cells

make up the majority of the thyroid tissue and secretes T3 and T4; these cells require iodine to produce T3 and T4

follicular cells

AKA parafollicular cells; secrete calcitonin

c cells

the main nerves of your parasympathetic nervous system; this system controls specific body functions such as your digestion, heart rate, and immune system; these functions are involuntary meaning you can’t consciously control them; AKA vagal nerves

vagus nerve

what are the anterior muscles also known as the strap muscles that surround the thyroid?

1\.) sternohyoid

2\.) omohyoid

3\.) sternothyroid

this is present in 10-40% of the population; it is a superior extension of the thyroid isthmus and is more common in the LT lobe

accessory or pyramidal lobe

the recurrent laryngeal nerve creates a pseudotumor along the posterior of the thyroid; not a nodule, normal thyroid tissue

zuckerkandl’s tubercle

the rate at which the body uses energy while at rest to maintain vital functions such as breathing and keeping warm

basal metabolism

what are thyroid secretions controlled by?

TSH

what is TSH and what is it secreted by?

thyroid-stimulating hormone (thyrotropin) and it is secreted by the anterior pituitary gland

what is the level of TSH regulated by?

the basal metabolic rate (BMR)

this results from a low concentration of thyroid hormones; triggers the hypothalamus to tell the pituitary gland to release TSH into the blood stream

decrease in BMR

what is the primary hormone secreted by the thyroid? (90%)

T4 (thyroxine)

what is the secondary hormone secreted by the thyroid? (10%)

T3 (triiodothyronine)

what is the primary function of the calcitonin secreted by the c cells?

to decrease the blood calcium levels, preventing hypercalcemia

what is the thyroid composed of?

follicles filled with colloid

small secretory cavity, sac, or gland

follicle

a gelatinous or mucinous substance found normally in the thyroid

colloid

a thyroid that is functioning normally and producing the correct amount of thyroid hormones

euthyroid

undersecretion of thyroid hormone; the most common thyroid disorder; most commonly caused by a chronic thyroid inflammatory process called Hashimoto’s thyroiditis

hypothyroidism

a rare, more severe complication of hypothyroidism that could lead to a life-threatening coma

myxedema

oversecretion of thyroid hormones; occurs when the thyroid is not functioning from Grave’s disease, overall thyroid enlargement, or localized adenoma causing oversecretion of thyroid hormones

hyperthyroidism

an extreme form of hyperthyroidism

thyrotoxicosis

congenital absence of the thyroid gland; may affect one lobe, the isthmus, or the entire gland; this has a severe affect on physical and mental development

aplasia

underdevelopment of any part of the thyroid gland; may be associated with congenital hypothyroidism

hypoplasia

may be present along embryologic descent if the thyroid migrates too little or too far; ectopic thyroid tissue locations include: posterior to the tongue, near the larynx, and mediastinal area; scintigraphy is ideal to visualize this

ectopic thyroid tissue

what are two tests used to determine thyroid function?

iodine uptake and thyroid scan

what shows more uptake of the tracer?

hyperactivity

what shows less uptake of the tracer?

hypothyroidism

a reporting system for thyroid nodules on ultrasound proposed by the american college of radiology

ti-rads

a general enlargement of the thyroid gland; longer than 6cm in length or thyroid parenchyma extending over the CCA in TRV

goiter

multiple nodules causing the thyroid to become enlarged

multinodular goiter

may affect large groups of people in a geographical area where iodine levels in the soil, food, and water are low; iodized salt usually corrects iodine insufficiency

endemic goiter

when enlargement of the gland is not associated with abnormal thyroid function

nontoxic goiter

when enlargement of the thyroid causes hyperthyroidism

toxic goiter

a true epithelial cyst in the thyroid is benign and uncommon

simple cyst

a cyst with a tiny echogenic focus; commonly has a comet tail artifact posterior to the echogenic focus; may be multiple

colloid cyst

a cyst that may have low-level echoes with debris present, wall irregularities, and internal septations

hemorrhagic cyst

a solitary, slow growing benign neoplasm

thyroid adenoma

a benign thyroid neoplasm that represents 5-10% of all thyroid nodules; 7x more likely in females

follicular adenoma

rare type of adenoma that have malignant cancer cells found after extraction

hurthle cell adenoma

a group of disorders that include inflammation of the thyroid gland with several causes including bacterial/viral infections, postpartum, post-radiation ablation technique, drug-induced, or autoimmune-related abnormalities

thyroiditis

typically caused secondary to a viral infection; diffuse inflammation of the thyroid with significant pain on thyroid palpitation, dysphagia, fever, thyroid enlargement, and malaise

de Quervians’s thyroiditis

an autoimmune disease in which the immune system attacks the thyroid and the thyroid responds by creating excessive thyroid hormones; the most common cause of hyperthyroidism; 5-8x more common in women after 30 years of age

grave’s disease

the most common form of thyroiditis caused by a destructive autoimmune disorder which leads to chronic inflammation of the thyroid

hashiomoto’s thyroiditis

rare cancer of the thyroid; there are 4 types: papillary, follicular, medullary, and anaplastic

thyroid carcinoma

most common thyroid cancer; considered the least aggressive type of tumor; females are affected more than males at age 20-40; major spread of this is through lymphatic channels

papillary carcinoma

second most common thyroid cancer; more aggressive than papillary carcinoma with a 20-year mortality rate of 20%; 3x more likely in females and seen between the ages of 40-60; NOT associated with radiation; there are 2 types: minimally invasive and widely invasive; spreads through the bloodstream

follicular carcinoma

accounts for 5-10% of thyroid cancers; develops from the c cells that secrete calcitonin; slightly higher female to male incidence (3-2) NOT associated with radiation

medullary carcinoma

rare thyroid cancer; considered the most deadly; 2x more likely in men after age 60; may be associated with radiation; usually diagnosed at stage 4 when found; this cancer grows quickly; typically causes death by asphyxiation due to invasion of the trachea

anaplastic carcinoma

what does anaplastic mean?

undifferentiated

term used to describe cells or tissues that do not have specialized structures or functions; these often grow and spread quickly

undifferentiated

the space remaining after a thyroid has been removed

the thyroid fossa

what are the parathyroids derived from?

endoderm cells

the stalk between the thyroid and the tongue

the thyroglossal duct

small, encapsulated, oval structures attached to the posterolateral surface of the thyroid glands; typically oval/bean shaped

parathyroid glands

what do parathyroids secrete?

PTH (parathyroid hormone)

what does PTH do?

maintains blood levels of calcium and phosphorus

where are the parathyroid glands located?

on the posterior surface of the thyroid gland

what is the approximate normal measurement of a parathyroid gland?

0\.5 x 0.3 x 0.1cm

what is the primary function of the parathyroid glands?

to help maintain homeostasis of blood calcium concentration

in the bones, what is calcium stored as?

phosphate

what decreases the concentration of calcium in the blood?

calcitonin

an endocrine disorder caused by increased function of the parathyroid gland; more common in women after age 40; characterized by abnormal secretion of PTH, which elevates calcium in the blood

primary hyperparathyroidism

a benign, solid mass and the most common cause of hyperparathyroidism; usually oval and solitary and can involve 1 or more parathyroid

parathyroid adenoma (PTA)

enlargement and hyperfunction of the parathyroid gland with no apparent cause

parathyroid hyperplasia

1% of pts with primary hyperparathyroidism have this

parathyroid carcinoma

occurs when the serum PTH level is increased due to chronic hypocalcemia

secondary hyperparathyroidism

most common congenital anomaly; 90% are found before age 10 in the pediatric pt

thyroglossal duct cyst

congenital cystic mass in the lateral neck in the submandibular region

branchial cleft cyst

localized or generalized enlargement of the lymph nodes

cervical lymphadenopathy (lymphomegaly)

identifies stiffness of tissues

elastography

what color do cold nodules appear to be in nuc med imaging? (scintigraphy)

lighter/white

what color do hot nodules appear to be in nuc med imaging? (scintigraphy)

darker/black

is this nodule hot or cold?

cold

is this nodule hot or cold?

hot

what thyroid pathology is shown here?

multinodular goiter

what thyroid pathology is shown here?

simple thyroid cyst

what thyroid pathology is shown here?

colloid cyst

what thyroid pathology is shown here?

hemorrhagic thyroid cyst

what thyroid pathology is shown here? note: these have a broad range of appearances and most often appear as solitary and homogeneous

thyroid adenoma

what thyroid pathology is shown here?

symptoms vary but may include mild-severe swelling, tenderness of the thyroid, symptoms of hypothyroidism

thyroiditis

what thyroid pathology is shown here?

characterized by three clinical findings: hypermetabolism, diffuse toxic goiter, and exophthalmos. Other symptoms include enlarged thyroid, thickening of the skin in the legs/feet, elevated T3/T4, and very low TSH

grave’s disease

what thyroid pathology is shown here?

young middle-aged woman; painless, diffusely enlarged thyroid; low serum T3/T4 and elevated TSH

hashimoto’s thyroiditis

what thyroid pathology is shown here?

palpable, firm, painless, solitary nodule in the thyroid; pt may present with cough, hoarseness, dysphagia, or dyspnea due to compression of adjacent neck anatomy

thyroid carcinoma

what thyroid pathology is shown here?

pts with hx of radiation are at increased risk; major spread is through lymphatic channels

papillary carcinoma

what thyroid pathology is shown here?

not associated with hx of radiation; spreads through bloodstream

follicular carcinoma