HYPERPARATHYROIDISM

✓ Medically ReviewedDISEASEID: MDBT0103🚨 TRIAGE: URGENTICD-10: E21.3

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Definition

CLINICAL DEFINITION

Hyperparathyroidism is excess parathyroid hormone (calcium-raising signal) with high blood calcium. Labs show high calcium with high or inappropriately normal PTH (gland signal). Phosphate (bone mineral) is often low from urinary loss. It is remembered by stones, bones, groans and psychic overtones (kidney, bone, gut and mood effects). Most primary cases reflect single adenoma (benign tumour). Secondary and tertiary forms follow chronic kidney disease (long kidney failure) and vitamin D lack.

IN PLAIN ENGLISH

Glands that control calcium work too much. Calcium in the blood gets high. High calcium can cause thirst and peeing. It can cause bone and belly pain. It needs fluid, calcium and gland care.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Hyperparathyroidism is not hypoparathyroidism (low hormone with low calcium) with tetany (hand spasms). It is not hypercalcaemia (high calcium) alone without PTH excess, such as cancer or vitamin D excess. It is not familial hypocalciuric hypercalcaemia (inherited benign high calcium) with low urine calcium and normal PTH effect. It is not hyperthyroidism (overactive thyroid) despite similar name and fatigue. Confirm with paired calcium and PTH plus phosphate and vitamin D.

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Word Breakdown

hyper-

=over or excess

parathyroid-

=parathyroid glands behind the thyroid

-ism

=state or condition

Literal Meaning: overactive parathyroid state

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Abbreviations

PTH=Parathyroid hormone - calcium-raising gland signal

Ca=Calcium - mineral for nerves, muscle and bone

CKD=Chronic kidney disease - long term kidney failure driving secondary excess

MEN=Multiple endocrine neoplasia - inherited tumour syndrome with parathyroid tumours

FHH=Familial hypocalciuric hypercalcaemia - inherited benign high calcium with low urine calcium

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Synonyms & Variants

Parathyroid overactivity›Hyperparathyroid state›Excess parathyroid hormone secretion›

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Category-Specific Context

Hyperparathyroidism is a Disease because it is lasting gland overactivity with course and complications. It is not a Symptom (felt complaint) such as thirst alone. It spans primary, secondary and tertiary forms (gland-first versus kidney-driven versus autonomous). Care targets cause removal and crisis prevention rather than symptom relief alone. It sits under calcium disorders with hypercalcaemia (high calcium) as its urgent face.

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Clinical Context & Usage

CLINICAL SETTINGS

Primary CareEndocrinology ClinicEmergency DepartmentAcute Medical UnitEndocrine Surgical Unit

USAGE & DOCUMENTATION NOTES

Use hyperparathyroidism for high calcium with high or inappropriately normal PTH, not thirst alone. Record calcium with albumin (binding protein), ionised calcium where available, phosphate, magnesium, vitamin D and kidney function. Document neck lumps, fractures, stones, lithium and thiazide use, family MEN (inherited tumour syndrome) and cancers. Do not label high calcium from cancer or vitamin excess alone without PTH pattern.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

PTH excess (extra gland signal) raises bone release and kidney reclaim of calcium. It wastes phosphate (bone mineral) in urine so blood phosphate falls. It raises calcitriol (active vitamin D) which lifts gut calcium uptake. High calcium causes thirst with polyuria (large urine volumes), constipation and confusion. Chronic excess thins bone, seeds kidney stones and stiffens vessels and gut.

PRIMARY CAUSES

Single parathyroid adenoma (benign tumour of one gland)

Clonal overgrowth secretes PTH despite high calcium so calcium rises with low phosphate

Multigland hyperplasia (enlargement of all glands)

Diffuse chief-cell excess (hormone-making cell growth) raises PTH set-point so calcium stays high

MEN1 with menin mutation (inherited tumour syndrome)

Parathyroid tumours plus pituitary and pancreatic tumours drive early recurrent PTH excess

MEN2A with RET mutation (inherited tumour syndrome)

Parathyroid hyperplasia plus medullary thyroid cancer (thyroid tumour) and phaeochromocytoma (adrenal tumour) with PTH excess

Chronic kidney disease with secondary drive

Low calcitriol (active vitamin D) plus phosphate retention (held mineral) and low calcium chronically stimulate all glands so PTH rises

Severe vitamin D deficiency with tertiary transformation

Chronic low gut calcium stimulates glands, then autonomous nodules (self-driving lumps) persist even after replacement or transplant

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Drug-Induced Causes

💊 Lithium (mood stabiliser) ↗

Mechanism: Shifts calcium-sensing receptor (blood calcium sensor) set-point so higher calcium is needed to suppress PTH, with gland hyperplasia on chronic use

→ Check calcium with PTH and lithium level, hydrate, review mood indication with psychiatry, consider switch, refer endocrine, avoid abrupt stop without cover

💊 Thiazide diuretics such as bendroflumethiazide, hydrochlorothiazide and indapamide ↗

Mechanism: Increase distal calcium reclaim (kidney calcium saving) and unmask primary excess so calcium rises

→ Check calcium with PTH and vitamin D, review blood pressure indication, hold or switch to non-thiazide per protocol, hydrate and recheck, refer if PTH stays high

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Epidemiology

Prevalence:Primary hyperparathyroidism is common in endocrine practice, especially in older adults. Secondary excess is common in chronic kidney disease (long kidney failure) and vitamin D deficiency. Tertiary disease clusters in long dialysis (kidney machine treatment) and post-transplant clinics. True rates vary by calcium screening and vitamin testing.

Age Group:All ages can be affected when cause is present. Primary single adenoma (benign tumour) clusters in middle-aged and older adults, often after menopause (stopped periods). Secondary forms follow kidney disease at any adult age. Genetic MEN (inherited tumour syndrome) presents in teens and young adults with family tumours.

Geographic Distribution:Hyperparathyroidism occurs worldwide without strong clustering. Primary detection tracks routine calcium screening and neck imaging access. Secondary patterns follow kidney failure and vitamin D deficiency burden. Referral centres see more MEN (inherited cases) and parathyroid surgery.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 URGENT

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

Hypercalcaemic crisis with dehydration and confusion
Acute kidney injury with polyuria and vomiting
MEN-associated pituitary, pancreatic and thyroid tumours
Parathyroid carcinoma with very high calcium and neck mass
Fragility fractures with severe osteoporosis

URGENT EVALUATION TRIGGERS

Calcium above critical threshold even if mild symptoms
Vomiting, polyuria, thirst or confusion with high calcium
Renal colic or stones with high calcium
Bone pain or fracture with high calcium
Short QT, palpitations or kidney injury with high calcium

Contraindications & Precautions

CONTRAINDICATIONS

Do not give thiazides or lithium without calcium monitoring in known excess
Do not give high-dose vitamin D or calcium supplements during high calcium without cause review
Do not give rapid discharge in crisis without fluids, kidney and ECG review
Do not arrange neck surgery without MEN, vocal cord and calcium workup

SPECIAL PRECAUTIONS

Check albumin-corrected and ionised calcium with PTH, phosphate, vitamin D and kidney function
Monitor fluids, urine output, pulse and ECG during crisis care
Watch bone density with kidney imaging for stones
Review lithium, thiazides, calcium and vitamin supplements at each visit
Counsel on thirst, polyuria, stones, bone pain and mood flags with emergency plan

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Kidney stones with colic (flank pain)
Nephrocalcinosis with kidney failure (kidney calcium deposits)
Osteoporosis with fractures (thin bones)
Hypercalcaemic crisis with dehydration and confusion
Pancreatitis with severe belly pain (pancreas inflammation)
Peptic ulcer with pain and bleeding (stomach sore)
Hypertension with vascular risk (high blood pressure)
Depression with fatigue and memory issues

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Reference Ranges

NORMAL RANGESerum total calcium 2.2 to 2.6 mmol per L and ionised calcium 1.15 to 1.33 mmol per L in most adult labs. PTH 1.6 to 6.9 pmol per L varies by assay.

CRITICAL (PANIC) VALUEAbove 3.0 mmol per L total calcium or any high calcium with vomiting, confusion, dehydration, kidney injury or ECG change needs emergency care.

UNIT OF MEASUREMENTmmol per L for calcium, pmol per L for PTH, with mg per dL in brackets for calcium.

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Hypoparathyroidism

Opposite condition sharing the stem but means low hormone with low calcium and tetany, not high hormone with high calcium and stones

Hyperthyroidism

Shares hyper prefix and gland wording but is thyroid overactivity with weight loss and tremor, not PTH excess with stones

Hypopituitarism

Similar sound and gland failure idea but is pituitary hormone lack with many axes, not parathyroid excess

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Malignancy-associated hypercalcaemia

Key Distinguishing Feature: High calcium with low PTH and known cancer with PTHrP (tumour signal) rather than high PTH

Familial hypocalciuric hypercalcaemia with CASR mutation

Key Distinguishing Feature: Lifelong mild high calcium with very low urine calcium and low clearance ratio that avoids surgery

Vitamin D intoxication with excess supplements

Key Distinguishing Feature: High calcium with low PTH and very high vitamin D that falls after stopping supplement

Sarcoidosis with granuloma calcitriol excess

Key Distinguishing Feature: High calcium with low PTH plus chest nodes (gland swellings) and high calcitriol rather than high PTH

Multiple myeloma with bone destruction

Key Distinguishing Feature: High calcium with low PTH plus anaemia, kidney failure and lytic lesions (bone holes) with monoclonal protein (abnormal antibody)

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Clinical Pearls

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Check paired calcium with PTH plus phosphate, magnesium, vitamin D and kidney function at diagnosis. High calcium with high PTH and low phosphate marks true excess.

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Give aggressive IV fluids (vein water) first for crisis with vomiting and confusion per protocol. Monitor calcium, kidney, ECG (heart tracing) and fluid balance closely.

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Calculate calcium-creatinine clearance ratio (urine calcium test) when FHH (inherited benign high calcium) is possible. Very low ratio favours FHH and avoids unneeded neck surgery.

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Review lithium and thiazides in every new high calcium and hold or switch per specialist. Recheck calcium with PTH after change to reveal hidden adenoma (benign tumour).

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Refer primary excess with stones, fractures, young age or marked calcium for parathyroidectomy (gland removal) assessment. Use cinacalcet (PTH-lowering drug) when surgery is not possible per endocrine plan.

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Example Usage & SOAP

CLINICAL SENTENCE

""58-year-old woman with stones and fatigue has hyperparathyroidism with high calcium.""

IN A SOAP NOTE

S: 58-year-old woman with thirst, polyuria, bone ache and constipation, no fever. O: Temp 36.9C, BP 148/88, HR 92, RR 18, SpO2 98 percent on air, dry mucosa, tender shins, no neck mass. Labs show high calcium with high PTH and low phosphate. A: Primary hyperparathyroidism with hypercalcaemia. P: Cardiac monitoring, IV fluids per protocol with kidney and ECG checks, hold thiazide, repeat calcium with PTH and vitamin D, neck ultrasound with sestamibi (gland scan), DEXA (bone test) and stone imaging, endocrine surgery review.

DIFFERENTIAL DIAGNOSIS CONTEXT

High calcium with high PTH favours hyperparathyroidism with low phosphate. High calcium with low PTH favours cancer or vitamin excess. Very low urine calcium favours FHH (inherited benign high calcium) over adenoma. High vitamin D with low PTH favours excess supplement. Check paired calcium with PTH plus vitamin D and urine calcium.

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Prognosis

SHORT-TERM OUTCOME

Mild high calcium often stays stable with fluids (vein water) and cause review. Crisis with vomiting, polyuria (large urine) and confusion can injure kidneys fast. Short QT (heart tracing change) with rhythm risk needs emergency monitoring. Early paired calcium with PTH plus fluids guides rescue.

LONG-TERM PROGNOSIS

Long term outlook is good after successful parathyroidectomy (gland removal) with bone and stone risk falling. Untreated excess causes recurrent stones, fractures and kidney decline. Tertiary disease after kidney failure has higher heart and bone risk. Regular calcium, kidney and bone checks shape course.

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References & Coding

ICD-10 DIAGNOSTIC CODE

E21.3

LITERATURE CITATIONS & GUIDELINES

[1]WHO ICD-10 E21 Hyperparathyroidism

[2]Endocrine Society primary hyperparathyroidism guidance

[3]Harrison's Principles of Internal Medicine calcium disorders

[4]NICE hypercalcaemia and parathyroid guidance

MEDICAL DISCLAIMER — This content is intended for educational purposes and qualified healthcare professionals only. Always refer to current clinical diagnostic criteria, institutional protocols, and official guidelines. Medobo is not responsible for clinical decisions made based on this content.