Primary Hyperparathyroidism

Slide 1 · Primary Hyperparathyroidism

Pathogenesis · morphology · clinicopathologic correlations

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Explain how autonomous PTH secretion produces hypercalcemia and phosphate loss.

Distinguish adenoma, primary hyperplasia, atypical neoplasm and carcinoma.

Relate genetic alterations to parathyroid lesions and familial syndromes.

Connect skeletal, renal and systemic pathology to biochemical findings.

A pathology-focused, mechanism-to-morphology lecture

Slide 3 · Four glands, variable locations

Schematic positions

Most glands lie near superior and inferior poles of each thyroid lobe.

Developmental descent permits ectopic glands, including thymic or mediastinal locations.

A functional parathyroid neoplasm may lie outside the usual cervical sites.

Anatomical variation matters when a lesion is being localized.

Slide 4 · Chief and oxyphil cells

Chief cells and stromal fat (schematic)

Chief cells predominate and contain secretory granules with PTH.

Oxyphil cells are larger, mitochondria-rich and conspicuously eosinophilic.

Normal adult parathyroid contains appreciable stromal adipose tissue.

Cell identity and stromal fat provide context for tumor morphology.

Slide 5 · Ionized calcium controls PTH

Low ionized Ca²⁺

Chief-cell PTH secretion

Plasma Ca²⁺ rises

Feedback inhibits PTH

Normal calcium feedback restrains parathyroid activity.

Slide 6 · Four actions of PTH

Kidney

Conserves calcium by increasing tubular reabsorption

Kidney / vitamin D

Promotes generation of active vitamin D

Urine / phosphate

Enhances phosphate excretion

Skeleton

Increases osteoclast-mediated resorption

The net effect is increased circulating ionized calcium.

Slide 7 · Renal calcium conservation

PTH increases

Renal tubular Ca²⁺ reabsorption

Calcium loss reduced

Circulating Ca²⁺ supported

PTH affects renal calcium handling before downstream tissue complications.

Slide 8 · Vitamin D amplifies calcium absorption

PTH signal

Renal activation of vitamin D

Increased gut Ca²⁺ absorption

Higher plasma Ca²⁺

The intestine is affected indirectly through renal vitamin D activation.

Slide 9 · Phosphate loss is part of the PTH signature

Excess PTH

Enhanced urinary phosphate excretion

Serum phosphate tends to fall

Less phosphate bound to Ca²⁺

Renal insufficiency may alter the expected phosphate concentration.

Slide 10 · Bone resorption raises blood calcium

Persistent PTH excess

Increased osteoclast activity

Mineralized bone resorbed

Ca²⁺ released to plasma

Long-standing signaling causes structural skeletal injury.

Slide 11 · Primary, secondary and tertiary hyperparathyroidism

Feature

Primary

Secondary

Tertiary

Driver

Autonomous PTH secretion

Compensatory PTH secretion

Autonomy after long-standing secondary disease

Typical setting

Parathyroid adenoma / hyperplasia

Renal disease or vitamin D deficiency

Prolonged secondary hyperparathyroidism

Pathophysiologic concept

Excess hormone despite high calcium

Response to persistent calcium-related stimulus

Acquired autonomy

Mechanism, rather than gland size alone, defines the category.

Slide 12 · Primary disease breaks normal feedback

Autonomous parathyroid lesion

PTH remains excessive / nonsuppressed

Serum calcium rises

Negative feedback fails to suppress PTH

Inappropriately normal PTH during hypercalcemia is not physiologically normal.

Slide 13 · Clinical epidemiology

Typical age

Most cases occur in adults aged 50 years or older

Sex distribution

Female predominance; Nearly 4:1

Reported incidence

Approximately 25 per 100,000 annually in the cited US/Europe data

Detection

Up to 80% found incidentally in outpatient laboratory tests

These are textbook estimates, not independently updated population statistics.

Slide 14 · Distribution of underlying parathyroid lesions

Adenoma

85–95% of cases

Primary hyperplasia

5–10% of cases

Carcinoma

Less than 1% of cases

Solitary sporadic adenoma is the dominant substrate.

Slide 15 · Adenomas are typically monoclonal

Most sporadic parathyroid adenomas are clonal neoplasms.

Autonomous growth and hormone production distinguish them from normal feedback-controlled tissue.

The two established recurrent adenoma pathways in the source are CCND1 dysregulation and MEN1 inactivation.

Clonality supports neoplasia; It does not by itself imply malignancy.

Slide 16 · CCND1 inversion places a growth gene near PTH control

PTH · 11p

CCND1 · 11q

PTH enhancer → CCND1

Mechanistic schematic — gene labels editable

Pericentromeric chromosome 11 inversion juxtaposes CCND1 with a PTH regulatory element.

CCND1 is normally at 11q; The PTH locus is at 11p.

The altered transcriptional context drives cyclin D1 overexpression.

This is an enhancer-position effect, not a PTH coding sequence change.

Slide 17 · Cyclin D1 overexpression promotes proliferation

CCND1 dysregulation

Cyclin D1 protein increases

Cell-cycle drive increases

Parathyroid cell expansion

Cyclin D1 overexpression can also occur without the inversion.

Slide 18 · Cyclin D1 dysregulation is not limited to inversion

Up to 40% of adenomas without CCND1 rearrangement overexpress cyclin D1.

Therefore, multiple upstream routes can converge on the same cell-cycle effector.

Finding cyclin D1 elevation alone does not demonstrate a specific chromosome inversion.

Distinguish a pathway readout from the underlying genomic lesion.

Slide 19 · MEN1 is a tumor-suppressor pathway

MEN1 · 11q13

Mutation + allelic loss

Mechanistic schematic — gene labels editable

About 15% of sporadic parathyroid tumors harbor somatic MEN1 alterations.

The MEN1 tumor-suppressor locus lies at chromosome 11q13.

Loss of heterozygosity of the second allele is described.

Germline MEN1 disease and sporadic somatic MEN1 alterations are different contexts.

Slide 20 · Two distinct sporadic adenoma mechanisms

Feature

CCND1 pathway

MEN1 pathway

Primary alteration

Gene juxtaposition / excess expression

Tumor-suppressor mutation and allelic loss

Protein-level consequence

Cyclin D1 upregulated

MEN1 tumor-suppressor function disrupted

Oncogenic logic

Growth drive increased

Growth restraint reduced

Both mechanisms can yield clonal parathyroid expansion.

Slide 21 · CDC73 links adenoma and carcinoma biology

CDC73 encodes parafibromin, a protein implicated in transcriptional regulation.

The source describes CDC73 alterations as frequent in sporadic parathyroid carcinomas.

CDC73 changes may also occur in some adenomas.

A molecular association is not equivalent to a standalone histologic malignancy criterion.

Retain the distinction between genetic risk and invasive behavior.

Slide 22 · Hyperparathyroidism–jaw tumor syndrome

Germline CDC73 alteration

Inherited predisposition

Parathyroid neoplasia

Ossifying jaw tumors may coexist

The syndrome includes a spectrum in which parathyroid carcinoma can occur.

Slide 23 · Familial syndromes occur less often than sporadic adenoma

The source identifies MEN-1, MEN-2 and MEN-4 in the familial setting.

Family history and other endocrine tumors can alter the diagnostic context.

Familial disease warrants a different interpretation from an isolated sporadic gland lesion.

The familial syndromes are noted here, not expanded beyond the source section.

Slide 24 · Familial hypocalciuric hypercalcemia: A mimic

Heterozygous CASR loss of function

Calcium sensing is less sensitive

PTH is not suppressed appropriately

Hypercalcemia without usual end-organ burden

FHH is a differential diagnosis, not simply another adenoma.

Slide 25 · Primary hyperparathyroidism versus FHH

Feature

Primary hyperparathyroidism

Familial hypocalciuric hypercalcemia

Origin

Autonomous PTH-producing lesion

Altered calcium sensing (often CASR)

PTH during high calcium

High or inappropriately normal

Nonsuppressed

Skeletal / renal effects

May be clinically significant

Usually lacks typical downstream burden

Interpretive point

Evaluate parathyroid pathology

Avoid reflex assumption of tumor

The textbook excerpt does not supply a urinary calcium ratio cutoff.

Slide 26 · Adenoma: Macroscopic morphology

Solitary circumscribed mass (schematic)

Usually one well-circumscribed, soft nodule.

Tan to reddish-brown cut surface; Typical reported weight 0.5–5 g.

Other parathyroid glands are often normal sized or reduced.

Gross circumscription and solitary distribution support adenoma.

Slide 27 · Adenoma may be ectopic

Ectopic site

Schematic positions

Adenomas can arise near the thyroid or at an ectopic site.

Anterior mediastinum is a documented ectopic location.

Failure to identify a cervical lesion does not exclude functioning parathyroid tumor.

Anatomic and functional localization should be interpreted together.

Slide 28 · Chief-cell adenoma: Uniform cellular sheets

Native schematic — not a photomicrograph

Sheets of polygonal chief cells with centrally placed nuclei.

Uniform architecture; Mitotic figures uncommon.

An edge of compressed nonneoplastic gland can be present.

Schematic of cellular relationships; Not a photomicrograph.

Slide 29 · Adenoma usually lacks obvious stromal fat

Native schematic — not a photomicrograph

Normal adult parathyroid commonly contains interspersed adipocytes.

In adenoma, stromal fat is inconspicuous.

A small remnant of compressed normal gland may retain fat.

Fat distribution is supportive, not a stand-alone determination.

Slide 30 · Adenoma: Uncommon cytologic variants

Chief-cell

Dominant conventional cell population

Oxyphil adenoma

Predominantly eosinophilic oxyphil cells

Water-clear adenoma

Predominantly clear cells

Chief-cell sheets remain the usual pattern.

Slide 31 · Endocrine atypia is not carcinoma

Occasionally, adenomas contain bizarre or pleomorphic nuclei.

This phenomenon is described as endocrine atypia.

Cytologic atypia alone does not establish invasive malignancy.

Confirm destructive invasion or metastasis before labeling carcinoma.

A high-value diagnostic pitfall in endocrine pathology.

Slide 32 · Normal gland versus adenoma

Observation

Normal parathyroid

Adenoma

Cellularity

Chief and oxyphil cells with stromal fat

Cellular chief-cell sheets

Stromal fat

Conspicuous in typical adult tissue

Often markedly reduced

Distribution

Four glands regulate calcium

Usually one discrete expanded nodule

Periphery

No tumor compression

Compressed normal rim may be present

These are patterns; Clinical and operative context remain essential.

Slide 33 · Primary hyperplasia: Often multiglandular

Multigland process (schematic)

Diffuse or nodular enlargement often affects all four glands.

Degree of enlargement can be asymmetric.

Combined gland weight rarely exceeds 1 g description.

Do not infer single-gland disease purely from asymmetry.

Slide 34 · Asymmetry complicates gland-level classification

Pattern A

Several glands enlarged: Hyperplasia favored

Pattern B

One gland much larger than others: Could still be asymmetric hyperplasia

Pattern C

One solitary adenoma with suppressed remaining glands: Adenoma favored

Morphologic overlap can require correlation with gland distribution.

Slide 35 · Primary hyperplasia: Cellular patterns

Native schematic — not a photomicrograph

Chief-cell hyperplasia is the common microscopic pattern.

Growth may be diffuse or multinodular.

Water-clear cells and oxyphil islands are recognized; Fat is reduced.

Native schematic illustrates pattern, not authentic histology.

Slide 36 · Adenoma and hyperplasia can overlap histologically

Feature

Adenoma

Primary hyperplasia

Typical gland count

Single gland

Multiple glands, sometimes asymmetric

Growth pattern

Well-circumscribed mass

Diffuse or multinodular

Stromal fat

Scarce

Scarce

Key pitfall

Single mass may dominate

An apparently spared gland does not rule it out

The number and behavior of glands can be more informative than cell appearance.

Slide 37 · Parathyroid carcinoma: Gross warning features

Irregular tumor (schematic)

Commonly one affected gland forming irregular gray-white mass.

Some lesions exceed 10 g description.

An infiltrative interface requires meticulous examination.

Large size and irregularity raise suspicion; Invasion confirms carcinoma.

Slide 38 · Carcinoma cytology often looks deceptively bland

Native schematic — not a photomicrograph

Tumor cells can be cytologically uniform and resemble normal cells.

Growth can be nodular or trabecular.

Cytologic detail by itself is unreliable for defining carcinoma.

Architectural invasion outweighs nuclear appearance.

Slide 39 · Defining carcinoma: Invasion or metastasis

Suspicious parathyroid lesion

Infiltrative growth into surrounding tissues OR metastasis

Malignant classification

Document the evidence

This is the defining criterion given, not pleomorphism alone.

Slide 40 · Pitfalls in diagnosing parathyroid malignancy

Not independently diagnostic

Strongly diagnostic in source

Large gland size

Invasion into surrounding structures

Cytologic pleomorphism

Demonstrated metastasis

Bizarre nuclei / endocrine atypia

Invasive growth pattern

Nodular architecture

Tumor spread beyond the primary site

The distinction prevents overdiagnosis of adenomas with endocrine atypia.

Slide 41 · Atypical parathyroid neoplasm

A category for neoplasms with worrisome, non-definitive features.

Fibrosis, cystic alteration and macronucleoli are examples given.

Such changes cannot substitute for documented invasion or metastasis.

The label preserves diagnostic uncertainty.

Suspicion is a different conclusion from proven carcinoma.

Slide 42 · Parafibromin loss and inherited predisposition

Parafibromin loss on IHC

Consider CDC73 alteration

Assess personal / family context

Evaluate germline CDC73 where indicated

Robbins calls for germline screening in parafibromin-deficient neoplasms or carcinoma.

Slide 43 · Four parathyroid lesions: Diagnostic logic

Lesion

Most useful distinguishing feature

Adenoma

Usually circumscribed solitary tumor

Primary hyperplasia

Usually multiglandular, diffuse or nodular

Atypical neoplasm

Worrisome features without definite invasion

Carcinoma

Invasive growth and/or metastasis

Histologic labels should correspond to evidence, not presumed biologic potential.

Slide 44 · Skeletal and renal injury explain the syndrome

Skeleton

Osteoclastic resorption → fragility and reparative lesions

Renal collecting system

Hypercalcemia favors urinary calculi

Renal parenchyma

Calcium deposition injures tubules and interstitium

Other organs

Severe hypercalcemia may cause metastatic calcification

Target-organ pathology reflects sustained PTH excess and hypercalcemia.

Slide 45 · Cortical bone bears major injury

Cortical / endosteal resorption (schematic)

Osteoclastic resorption predominantly affects cortical surfaces.

Subperiosteal and endosteal bone are particularly involved.

Bone mass falls, increasing susceptibility to fractures.

The reported cortical predominance is a feature of skeletal involvement.

Slide 46 · Dissecting osteitis: Resorption tunnels

Longitudinal trabecular tunnels (schematic)

Osteoclasts tunnel longitudinally through medullary trabeculae.

The resulting tracks may resemble railroad rails.

Surrounding marrow spaces develop fibrovascular tissue.

Schematic rendering of the described destructive process.

Slide 47 · Brown tumors are reactive, not epithelial cancer

Excess bone resorption

Microfracture and hemorrhage

Macrophages + reparative fibrous tissue

Brown tumor mass

Hemosiderin, hemorrhage and vascularity explain the brown color.

Slide 48 · Osteitis fibrosa cystica is a composite lesion

Bone resorption

Increased osteoclast action

Peritrabecular response

Fibrous stromal replacement

Cystic / hemorrhagic lesions

Brown tumors may undergo cystic change

Severe, untreated disease combines all three processes.

Slide 49 · Mechanism-to-lesion sequence in bone

Autonomous PTH secretion

Sustained osteoclast activity

Weakened / microfractured bone

Fibrosis and brown tumors

The same pathway links biochemical abnormality to morphologic damage.

Slide 50 · Nephrolithiasis reflects high calcium burden

Discrete urinary stones (schematic)

PTH-driven hypercalcemia promotes renal tract stone formation.

Stones can cause pain and obstructive uropathy.

Chronic renal injury can complicate prolonged disease.

Renal stones are an end-organ manifestation, not the cause of primary autonomy.

Slide 51 · Nephrocalcinosis is distinct from stones

Parenchymal deposits (schematic)

Calcium deposition may involve renal interstitium and tubules.

Unlike a discrete urinary calculus, this is parenchymal calcification.

Kidney injury can alter phosphate handling and clinical manifestations.

Separate parenchymal mineralization from collecting-system calculi.

Slide 52 · Metastatic calcification can involve multiple organs

Stomach

Visceral calcium deposits in severe disease

Lung

Pulmonary tissue may accumulate calcium

Heart

Myocardial and valvular abnormalities may occur

Blood vessels

Vascular mineralization can occur

Here “metastatic calcification” denotes calcium deposition, not tumor metastasis.

Slide 53 · Two modes of presentation

Feature

Asymptomatic detection

Symptomatic disease

Recognition

Incidental elevated serum calcium

Clinical effects of high calcium / PTH

Morphologic burden

Often no severe bone / renal lesions

May include stones, skeletal disease, organ calcification

Diagnostic implication

Biochemical evaluation is decisive

Exclude nonparathyroid causes of hypercalcemia

Biochemical screening shifted detection away from advanced manifestations.

Slide 54 · Why classical lesions are now less frequent

Routine chemistry testing

Incidental calcium elevation

Earlier recognition of PHPT

Fewer advanced skeletal / renal lesions

That osteitis fibrosa cystica and brown tumors are less commonly encountered today.

Slide 55 · Painful bones, renal stones, abdominal groans…

Bones

Pain and fractures from loss of skeletal integrity

Stones

Nephrolithiasis and obstruction

Abdomen

Constipation, nausea and other GI complaints

Psychic moans

Mood, consciousness and CNS symptoms

The mnemonic compresses several pathophysiologic pathways.

Slide 56 · Gastrointestinal and neuromuscular manifestations

Feature

Gastrointestinal

Neuromuscular

Common in source

Constipation, nausea

Fatigue and weakness

Also described

Peptic ulcers, pancreatitis, gallstones

Reduced functional capacity

Link to disease

Systemic effect of excess PTH / calcium

Systemic effect of hypercalcemia

Symptoms are clinically relevant but nonspecific in isolation.

Slide 57 · Neurologic and cardiovascular involvement

Neuropsychiatric

Depression and lethargy

Severe CNS involvement

Seizures can occur in advanced manifestations

Cardiac / valvular

Aortic or mitral valvular calcification

Clinical synthesis

Hypercalcemia can produce multisystem disease

Symptom severity does not identify the underlying gland lesion by itself.

Slide 58 · Malignancy: Major competing cause of hypercalcemia

Malignancy is described as the leading cause of symptomatic hypercalcemia in adults.

Solid tumors and hematologic malignancies may produce hypercalcemia.

PTH-related peptide-mediated bone resorption is a major mechanism in solid-tumor settings.

Nonparathyroid hypercalcemia usually suppresses endogenous PTH.

Do not diagnose PHPT from high calcium alone.

Slide 59 · Biochemistry separates PTH-dependent causes

Interpret circulating PTH during hypercalcemia

Elevated or inappropriately normal PTH

Supports a PTH-dependent process

Consider PHPT and mimics such as FHH

Low or undetectable PTH

Supports PTH-independent hypercalcemia

Evaluate malignancy and other etiologies

During hypercalcemia, PTH should be physiologically suppressed.

Slide 60 · Typical biochemical pattern of PHPT

Serum calcium

Increased

PTH

Elevated or inappropriately normal

Phosphate

Often decreased from phosphaturia

Urine

Calcium and phosphate excretion increased in the source description

Renal disease can obscure the anticipated low serum phosphate.

Slide 61 · Hypercalcemia: A mechanism-based differential

Feature

PTH not suppressed

PTH suppressed

Typical categories

Primary / tertiary hyperparathyroidism; FHH

Malignancy; Vitamin D excess

Other examples

Assess disease context

Granulomatous disease; Immobilization

Additional medication context

Interpret thiazide exposure clinically

Medication effects need clinical correlation

Table is a conceptual regrouping of Robbins Table 24.5; No laboratory cutoffs supplied.

Slide 62 · Localization is not the biochemical diagnosis

Biochemical evidence of PHPT

Clinical gland-localization question

99mTc-sestamibi scintigraphy

Localization may support planning

Robbins Fig. 24.24 illustrates uptake in a left inferior adenoma.

Slide 63 · Application case: Incidental hypercalcemia

An otherwise well adult has elevated calcium on routine blood chemistry. Intact PTH is not suppressed.

Interpretive questions

Why is a nonsuppressed PTH abnormal in this biochemical context?

What parathyroid lesion is most probable?

Which mimic should be considered before assuming a surgically removable tumor?

Slide 64 · Case interpretation: Autonomy versus altered sensing

Feedback logic

Calcium elevation normally suppresses PTH

Most likely morphology

A solitary sporadic adenoma is the commonest cause

Important mimic

FHH can produce calcium elevation with nonsuppressed PTH

A lesion diagnosis needs the correct clinical and biochemical context.

Slide 65 · Application case: A suspicious parathyroid tumor

A resected parathyroid mass contains relatively bland, uniform cells, focal fibrosis and prominent nuclei. No invasion or metastasis is documented.

Interpretive questions

Can cytologic blandness exclude carcinoma?

Do fibrosis and macronucleoli alone prove malignancy?

Which evidence would be required for a definitive carcinoma diagnosis?

Slide 66 · Case interpretation: Prove invasion

Bland nuclei

Compatible with carcinoma; Not exclusionary

Fibrosis and macronucleoli

May support an atypical neoplasm label

Definitive evidence

Invasion into surrounding tissue and/or metastasis

Document the demonstrated criterion rather than infer malignant behavior.

Slide 67 · Integrated pathologic interpretation

Autonomous gland lesion

PTH-related Ca²⁺ and phosphate shifts

Target-organ responses

Morphology + biochemical correlation

A credible diagnosis connects mechanism, lesion type and clinical consequences.

Slide 68 · Core conclusions

Solitary adenoma accounts for most primary hyperparathyroidism.

CCND1 and MEN1 drive sporadic adenoma biology; CDC73 is important in carcinoma-associated risk.

Invasion or metastasis—not endocrine nuclear atypia—defines carcinoma.

Skeletal resorption, urinary stones and tissue calcification explain the systemic phenotype.

PTH during hypercalcemia anchors the biochemical differential.

Interpret morphology together with feedback physiology and disease context.

Slide 69 · Principal reference

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. Elsevier; 2026.

Chapter 24: The Endocrine System — Parathyroid Glands and Primary Hyperparathyroidism, pp. 993–996.

The source text was available as an extracted Markdown conversion. Original textbook figure panels and chapter PDF were not supplied; all illustrations here are native schematics.