Parathyroid Fx Normal Dx Anatomy Multimodality Applied Anatomy
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Artistic Rendering – Normal Parathyroid Glands Artistic rendering depicts the four parathyroid glands — two superior and two inferior — located posteriorly within the thyroid gland. The parathyroids are relatively small glands in contrast with the dominant structure of the thyroid, However despite their small size their function is essential to calcium and phosphate metabolism Courtesy: Ashley Davidoff MD, TheCommonVein.com (993852.d03cd01 parathyroid normal)
2. Definition
Page 2 – Definition
Definition
The parathyroid glands are small endocrine glands, typically four in number, embedded on the posterior surface of the thyroid gland. They regulate calcium and phosphate metabolism through secretion of parathyroid hormone (PTH).
Aspect
Details
Structure
Small, oval glands on the thyroid’s posterior surface
Supplementation or parathyroidectomy depending on cause
3. Anatomy
Page 3 – Applied Anatomy and Diagnostic Approach
U-SSPCT–C Table
Feature
Details
Units
4 glands: R sup, R inf, L sup, L inf
Size
~6mm x 3–4mm x 1–2mm
Shape
Oval
Position
Posterior to thyroid
Character
Soft, yellow, vascular
Time
Functional by week 5–6 gestation
Connections
See subtable
Connections (Bullet-Pointed Units)
Type
Details
Arterial Supply
• Inferior thyroid artery
• Occasionally superior thyroid artery
Venous Drainage
• Thyroid venous plexus
• Internal jugular vein
Lymphatics
• Deep cervical nodes
• Paratracheal nodes
Nerve Supply
• Cervical sympathetic chain
• No parasympathetic innervation
Ducts
• None
Imaging Modalities
Modality
Primary Use
When/Why Used
Ultrasound
Identify adenomas
First-line tool
Sestamibi Scan
Localizes active adenomas
Surgical planning
4D-CT
Structural + perfusion
Re-operations or ectopics
MRI
Alternative
Complex cases
Laboratory Tests
Test
Purpose
Use
Calcium
Detect hyper/hypocalcemia
Basic screening
PTH
Functional test
Confirms PTH status
Phosphate
Tracks inverse relation
Supplementary
Vitamin D
Co-factor
Diagnostic clarification
Other Tools
Tool
Use
Indication
DEXA
Bone density
Chronic elevation
Intra-op PTH
Confirms adenoma removal
During surgery
4. Disease and Diagnosis
Page 4 – Clinical Diagnosis (Updated)
1. Pathology by TCV Disease Categories (IINMTM)
Category
Disease Example(s)
1. Inflammatory and Immune
Autoimmune hypoparathyroidism (e.g., part of APS-1)
2. Infection
Rare—Tuberculosis or fungal infections may rarely affect parathyroids
3. Neoplasm – Benign
Parathyroid adenoma (most common cause of primary hyperparathyroidism)
4. Neoplasm – Malignant (Primary)
Parathyroid carcinoma (rare but aggressive)
5. Neoplasm – Malignant (Metastatic)
Metastasis to parathyroid is exceedingly rare
6. Mechanical
Compression of glands in thyroid surgery or goiter
7. Trauma
Surgical trauma leading to hypoparathyroidism after thyroidectomy
8. Metabolic
Secondary hyperparathyroidism due to chronic kidney disease
9. Circulatory
Ischemic injury post-thyroid surgery
10. Inherited
MEN1 and MEN2A syndromes with parathyroid adenomas/hyperplasia
11. Infiltrative
Hemochromatosis or sarcoidosis affecting gland function
12. Idiopathic
Isolated idiopathic hypoparathyroidism (no autoimmune or surgical cause)
13. Iatrogenic
Accidental removal or injury during thyroid/parathyroid surgery
14. Functional
Pseudohypoparathyroidism (resistance to PTH at receptor level)
15. Psychiatric
None directly; psychiatric symptoms may result from calcium imbalance (e.g., depression in hypocalcemia)
2. Clinical Signs and Symptoms
Symptom
Interpretation
Fatigue, weakness
Common in hypercalcemia
Bone pain/fractures
Bone resorption due to elevated PTH
Kidney stones
Hypercalciuria in hyperparathyroidism
Abdominal pain, constipation
Hypercalcemia effect on GI tract
Muscle cramps, tetany
Hypocalcemia from low PTH
Chvostek and Trousseau signs
Classic signs of hypocalcemia
Cognitive slowing or depression
Seen in chronic calcium imbalance
3. Imaging Modalities
Modality
Primary Use
When/Why Used
Neck Ultrasound
Identify adenomas (hypoechoic nodules)
First-line in workup of hyperparathyroidism
Sestamibi Scan
Functional imaging of hyperactive gland(s)
Guides surgical approach
4D-CT
Combines anatomic and perfusion detail
Helpful in complex cases or re-operations
MRI
Soft tissue contrast; for ectopic/complex localization
Used when other imaging is inconclusive
4. Laboratory Tests
Test
Purpose
When/Why Used
Serum calcium
Assess hyper- or hypocalcemia
First-line diagnostic test
Serum phosphate
Inversely related to calcium in many cases
Hypophosphatemia in hyperparathyroidism
Intact PTH
Directly measures parathyroid hormone
Core diagnostic test
Vitamin D
Co-factor in calcium metabolism
Important for interpretation of calcium-PTH axis
Creatinine/BUN
Evaluate renal function
Secondary hyperparathyroidism evaluation
5. Other Diagnostic Tools
Tool
Use
Indication
DEXA Scan
Bone density assessment
Long-standing hyperparathyroidism
Intraoperative PTH monitoring
Confirm removal of hyperfunctioning tissue
Used during parathyroidectomy
Genetic testing (MEN syndromes)
Screen for familial forms
In patients with syndromic or early-onset disease
Calcium/Creatinine Clearance Ratio
Differentiate FHH (familial hypocalciuric hypercalcemia) from PHPT
Used in borderline lab cases
5. History and Culture
Page 5 – History, Culture, and Art (Updated and Expanded)
1. History of Anatomy
Topic
Details
First Identification
Discovered in 1850 by Sir Richard Owen in the Indian rhinoceros
Human Identification
Ivar Sandström described human parathyroid glands in 1880
Anatomic Understanding
Initially confused with thyroid nodules; later confirmed as distinct endocrine structures
2. History of Physiology
Milestone
Details
Early Insight
Role in calcium metabolism observed through tetany after thyroid surgery
Experimental Work
20th-century studies in dogs and humans identified PTH’s role in bone resorption and renal function
Modern Understanding
PTH identified as key hormone in calcium homeostasis, interacting with kidneys, bones, and vitamin D pathways
3. History of Diagnosis
Era
Diagnostic Development
Pre-20th Century
Diagnosis inferred from tetany and bone deformities
Mid-20th Century
Serum calcium and phosphate assays introduced
Late 20th Century
Intact PTH assays revolutionized differentiation of primary vs secondary hyperparathyroidism
4. History of Imaging
Modality
Development and Significance
Ultrasound
Became standard for neck mass detection and parathyroid adenoma localization
Sestamibi Scintigraphy
Introduced in 1989; revolutionized pre-op localization
4D-CT
Recent high-resolution, perfusion-based modality offering detailed anatomic and vascular mapping
5. History of Laboratory Testing
Test
Advancement
Serum Calcium
First major clue in parathyroid disorders
PTH Assay
Radioimmunoassay in 1960s, now standard with second-generation “intact” PTH tests
Vitamin D
Included for assessing secondary causes or vitamin D–dependent regulation
6. History of Therapies
Period
Therapeutic Development
1925
First parathyroidectomy by Felix Mandl
1950s–60s
Vitamin D analogs and calcium salts for hypoparathyroidism
2000s
Cinacalcet and calcimimetics introduced; minimally invasive parathyroidectomy now standard
7. Cultural Meaning
Theme
Representation
“Small but Mighty”
The parathyroids are metaphorically linked to overlooked power—tiny structures controlling vital mineral balance
Symbol of Fragility
Their silent influence on bones and nerves often makes them symbolic of hidden strength or silent collapse
Medical Lore
Known as the “hidden glands” — small, easily injured during thyroid surgery yet vitally important
8. Artistic Representations
Work or Theme
Description
Anatomical Models
Rare standalone parathyroid depictions; usually shown with thyroid in surgical or digital models
Symbolic AI Renderings
Emerging interest in using metaphorical art to visualize parathyroid function (e.g., gatekeeper balancing calcium)
Sculpture and VR
Medical education is beginning to adopt 3D-printed parathyroid models for spatial orientation and teaching
9. Notable Figures
Name
Contribution
Richard Owen
First described the parathyroid in animals
Ivar Sandström
Identified parathyroid glands in humans
Felix Mandl
Performed the first curative parathyroid surgery
Fuller Albright
Pioneered work in calcium-phosphorus metabolism and parathyroid disorders
10. Quotes
Quote
Attribution
“The parathyroids are like whispers in the endocrine symphony—but remove them, and the silence is deafening.”
Anonymous Endocrinologist
“Sometimes the smallest gland can wield the greatest balance.”
TCV Metaphor
7. MCQ's
Page 6 – MCQs
Basic Science Question 1
Which embryological pouches give rise to the parathyroid glands? A. First and second B. Second and third C. Third and fourth D. Fourth and sixth
Correct Answer Table
Correct Answer
Explanation
C. Third and fourth
Superior parathyroids derive from the 4th pouch; inferior from the 3rd, due to their migration.
Incorrect Answers Table
Option
Why Incorrect
A
These form parts of the ear and oral cavity
B
Second pouch forms palatine tonsils
D
Sixth pouch is not involved in parathyroid formation
Basic Science Question 2
Which hormone opposes the action of parathyroid hormone (PTH)? A. Calcitonin B. Cortisol C. Insulin D. Glucagon
Correct Answer Table
Correct Answer
Explanation
A. Calcitonin
Calcitonin lowers serum calcium by inhibiting osteoclasts, opposing PTH action.
Incorrect Answers Table
Option
Why Incorrect
B
Cortisol affects bone but doesn’t directly oppose PTH
C
Insulin regulates glucose, not calcium
D
Glucagon influences glucose, not calcium metabolism
Clinical Question 1
Which of the following is a classic complication of untreated primary hyperparathyroidism? A. Hyperkalemia B. Osteoporosis C. Addison’s disease D. Hypernatremia
Correct Answer Table
Correct Answer
Explanation
B. Osteoporosis
Elevated PTH increases bone resorption, leading to osteoporosis.
Incorrect Answers Table
Option
Why Incorrect
A
Hyperkalemia is not a feature of PTH excess
C
Addison’s disease affects adrenal glands
D
Hypernatremia is not related to PTH function
Clinical Question 2
A patient with parathyroid carcinoma is most likely to present with: A. Hypocalcemia B. Hypercalcemia C. Anemia D. Bradycardia
Correct Answer Table
Correct Answer
Explanation
B. Hypercalcemia
Excessive PTH from carcinoma causes severe hypercalcemia.
Incorrect Answers Table
Option
Why Incorrect
A
Hypocalcemia occurs in hypoparathyroidism
C
Anemia is not typical of parathyroid disease
D
Bradycardia not commonly associated with PTH levels
Radiology Question 1
What is the hallmark finding of parathyroid adenoma on a Sestamibi scan? A. Cold nodule B. Persistent radiotracer uptake C. No uptake D. Delayed washout
Correct Answer Table
Correct Answer
Explanation
B. Persistent radiotracer uptake
Adenomas retain sestamibi longer than thyroid tissue.
Incorrect Answers Table
Option
Why Incorrect
A
Adenomas are “hot”, not cold
C
Lack of uptake occurs in scar or cyst
D
Adenomas have persistent uptake, not delayed washout pattern
Radiology Question 2
Which modality is most sensitive in detecting ectopic parathyroid glands? A. Neck ultrasound B. MRI C. 4D-CT D. Plain X-ray
Correct Answer Table
Correct Answer
Explanation
C. 4D-CT
Combines anatomy and perfusion for high sensitivity in ectopic gland detection.
Incorrect Answers Table
Option
Why Incorrect
A
Poor at detecting ectopic locations
B
MRI is less spatially detailed for this purpose
D
X-rays do not visualize soft tissue glands
Radiology Question 3
In ultrasound imaging, a typical parathyroid adenoma appears as: A. Isoechoic nodule B. Hyperechoic lesion C. Hypoechoic, oval lesion posterior to thyroid D. Calcified mass within trachea
Correct Answer Table
Correct Answer
Explanation
C. Hypoechoic, oval lesion posterior to thyroid
Classic sonographic appearance of adenoma.
Incorrect Answers Table
Option
Why Incorrect
A
Parathyroid adenomas are usually hypoechoic
B
Hyperechoic features are rare
D
Tracheal calcifications are unrelated to parathyroid disease
8. Memory Image
Page 7 – Memory Image
Title
Description
Attribution
The Calcium Keeper
AI-generated metaphor of a castle’s gatekeeper gently balancing calcium stones at the gates of a fortress representing the skeleton and kidneys, illustrating the parathyroid’s regulatory control.
AD AI – Modified AI image by Ashley Davidoff MD, TheCommonVein.com (140541.endocrine)
