Parathyroid Anatomy and USA w/Pathology

How many parathyroid glands do we have?

4

Parathyroid is located…

In the mid and lower posterior regions of the thyroid

The inferior pair of parathyroid glands are usually more ________ than the superior pair

Anterior

Parathyroid gland shape

Disc/bean

Normal parathyroid measurements

Length: 5-7mm

Width: 3-4mm

AP: 1-2mm

Parathyroid hormone and calcitonin control…

Calcium absorption/excretion in the intestines and kidneys

Increased serum levels of calcium leads to …

Hypercalciuria and hypercalcemia

Low calcium levels in the blood leads to:

Increase in release of PTH

Decrease in the release of calcitonin

Reduced excretion of calcium in intestinal tract to increase the level of calcium in the blood

Kidneys increase resorption of calcium during blood filtration

End result = increasing calcium serum levels

High calcium levels in the blood leads to:

Decrease in the release of PTH

Increase in the release of calcitonin

Increased excretion of calcium in the intestines to reduce the level of calcium in the blood

Kidneys reduce calcium resorption during blood filtration

End result = reduced calcium levels in blood

Parathyroid pt position

Pts neck is hyperextended and turned away from the side being examined

Superior parathyroid gland is usually located …

Posterior to the midsegment of the thyroid lobe

Inferior parathyroid gland is usually located …

Close to the lower pole of the thyroid lobe

Parathyroid glands may be found __________ the clavicles, in the lower neck, upper mediastinum or retroplacental in location

Below

Parathyroid normally appears as…

A subtle hypoechoic area adjacent to the lower 2/3rds of the thyroid gland

Hyperparathyroidism

Increased function of the parathyroid glands

Common in women after menopause

Primary hyperparathyroidism most commonly occurs due to

Single adenoma in one parathyroid gland

Primary hyperparathyroidism is the most common classification of:

Multiple endocrine neoplasm (MEN) syndrome

Primary hyperparathyroidism is associated with

Hypertension, nephrolithiasis, osteopenia, weakness, malaise, dyspepsia, constipation, polyuria

Renal calculi formation due to chronic serum hypercalcemia in blood

Primary hyperparathyroidism

PTH secretion is constantly induced by the adenoma, which causes parathyroid gland hyperplasia

Parathyroid hormone will counteract the production of calcitonin

Increasing PTH increases serum calcium levels

Increasing calcitonin reduced serum calcium levels

Increased PTH reduced vitamin D storage, causes deficiency

Increased levels of PTH cause increased renal excretion of phosphate = reduced serum phosphate levels

Calcitonin

Is a hormone produced by the parafollicular cells of the thyroid that is responsible for calcium metabolism and excretion

Increased levels of _____ and calcium in the blood

PTH

Secondary hyperparathyroidism

All 4 glands hyperfunctioning

Usually caused by renal failure, also vitamin D deficiency, malabsorption syndromes

Failing kidneys cannot remove phosphorus from the blood which caused calcium levels to drop

PTH production is increased as the body tried unsuccessfully to raise calcium levels

Low serum calcium with high PTH levels seen early in the disease progression

Secondary hyperparathyroidism = _________calcemia

Hypo

Primary hyperparathyroidism = ________calcemia

Hyper

Most common hyperparathyroidism

Primary

Ectopic parathyroid tissue

Found in 15-20% population

75% found near thymus gland near heart

Can be found within the thyroid tissue

May also fail to descend far enough and remain by carotid arteries and/or esophagus

Most common cause of primary hyperparathyroidism

Parathyroid adenoma

Parathyroid adenoma

Benign nodule varying in size, usually less than 3cm, average is 1cm

Usually occur in a single gland

Scintigraphy, MRI, and CT exams can also be used to localized parathyroid adenomas

FNA Bx can be used to definitively diagnose the presence of an adenoma

USA parathyroid adenoma

Oval-shaped, hypoechoic, encapsulated, homogeneous, solid mass

May resemble thyroid adenomas but protrude off POSTERIOR surface of thyroid

Hypervascular masses

Vascular Arc - vascularity surrounds 90-270 degrees around mass

Parathyroid adenoma

Parathyroid carcinoma

Rare, slow growing

Increased risk with MEN syndrome and neck radiation

Variable sonographic appearance

Parathyroid carcinoma Symptoms

Bone pain, constipation, fatigue, frequent thirst, frequent urination, kidney stones, muscle weakness, N/V, poor appetite

USA Parathyroid carcinoma

Small, irregular, firm masses

Usually larger than benign adenomas

Taller than wide shape correlates with malignancy

May adhere to surrounding tissues

Varied echogenicity

Mets to regional nodes or distant organs may occur

Normal Lymph nodes

Thin disk or bean shaped

<1cm diameter

Hypoechoic rim with echogenic center

Normal lymph nodes do NOT exhibit posterior enhancement

Lymph nodes

Enlarged nodes are non-specific finding

Seen with infection, lymphadenopathy, mets

Pts with prior hx of thyroid cancer and/or thyroidectomy due to cancer should be evaluated regularly

Abnormal lymph nodes

Rounded or plump appearance

Cortex will become more hypoechoic or may even be anechoic due to increase in fluid

Edematous nodes will exhibit posterior enhancement

Central hilum disappears with enlargement

Blood flow to hilum will increase

Parotid gland

Largest saliva gland; located anterior to the ear, wrapped around the mandibular ramus; Stensen duct carries saliva into mouth

Submandibular glands

Located under the mandible; Wharton duct carries saliva into mouth

Sublingual glands

Located under tongue

Salivary glands

Parotid, submandibular, sublingual

Salivary glands are supplied blood by ___________ and drained into the IJV

Branches of the ECA

Saliva contains _________

Amylase

Sialolithiasis

Stones form within the gland or duct or oral cavity

May see posterior shadowing

If stone causing obstruction, the duct will be dilated within the gland

Infection of the salivary glands causes…

Enlarged glands with decreased echogenicity

Most common infection of the salivary glands and affects parotid glands

Mumps

Bilateral salivary gland enlargement usually indicates:

Infectino

Unilateral salivary gland enlargement usually indicates:

Mass formation

Most common malignancy in salivary glands

Mucoepidermoid carcinoma

Sjogren syndrome

Immune system disorder causes a reduction in saliva production

Associated with rheumatoid arthritis and lupus

Primary symptoms are dry eyes and dry mouth

Usually affects the parotid and submandibular glands

May cause swelling of the salivary glands

Sialolithiasis

Normal submandibular salivary gland

Acute parotitis/mumps infection

Sjogren syndrome

Salivary malignancy

As levels of the parathyroid hormone increase, how are serum calcium levels affected?

Increased

As levels of calcitonin increase, how are serum calcium levels affected

Decreased

Scan the area extending from the _________ superiorly to the __________ inferiorly to locate the parathyroid glands

CCA bifurcation; thoracic inlet

What may assist in localizing the parathyroid gland?

Ask the pt to swallow, place focal zone deep to the thyroid, use graded compression

Primary hyperparathyroidism most commonly occurs due to:

Single adenoma in one parathyroid gland

Secondary hyperparathyroidism most commonly occurs due to:

4 hyperfunctioning glands

Hypophosphatemia is associated with:

Increased PTH levels

Which of the following indicates secondary parathyroidism

High serum calcium with high PTH levels

Low serum calcium with high PTH levels

Low serum calcium with low PTH levels

High serum calcium with low PTH levels

Low serum calcium with high PTH levels

What causes an increased risk of parathyroid cancer?

MEN syndrome and neck radiation

Which of the following is a symptom of primary parathyroidism

Frequent thirst

Lack of urination

Kidney cysts

All of the above

Frequent thirst

Parotid gland is located _______ to the ear

Anterior