```html

Juvenile Hyperparathyroidism – A Comprehensive Guide

Overview

Juvenile hyperparathyroidism (JHP) is a rare disorder in which one or more of the parathyroid glands produce too much parathyroid hormone (PTH) in children and adolescents (< 21 years). The excess hormone drives the body’s calcium level upward, leading to a cascade of metabolic and skeletal problems.

Although “hyperparathyroidism” is more commonly diagnosed in adults over 50 years, JHP accounts for < 1 % of all primary hyperparathyroidism cases <sup>[1]</sup>. Reported incidence is roughly 2–5 cases per million children per year, but exact numbers vary because many cases are mis‑diagnosed as other calcium‑related disorders.

Both boys and girls are affected, though a slight female predominance (≈55 % female) has been noted in several case series <sup>[2]</sup>. The condition can appear at any age from infancy to late adolescence, with a median age of diagnosis around 12 years.

Symptoms

Symptoms result from high calcium (hyper‑calcemia) and from the underlying effects of PTH on bone, kidneys, and the gastrointestinal (GI) tract. Not every child will have all of these signs, and many are subtle at first.

General/Systemic

• Fatigue and weakness – often described as “tiring easily” or “slower recovery after activity.”
• Polyuria and polydipsia – frequent urination and excessive thirst due to calcium‑induced nephrogenic diabetes insipidus.
• Dehydration – secondary to fluid loss from polyuria.
• Weight loss – despite normal or increased appetite.
• Headaches or cognitive difficulties – “brain fog,” difficulty concentrating, irritability.

Skeletal & Muscular

• Bone pain – often in the long bones, ribs, or pelvis.
• Fractures – low‑impact or pathologic fractures due to osteitis fibrosa cystica.
• Deformities – bowed limbs or scoliosis in severe, longstanding disease.
• Muscle cramps or twitching – calcium’s effect on neuromuscular excitability.

Kidney‑Related

• Kidney stones (nephrolithiasis) – flank pain, hematuria.
• Nephrocalcinosis – calcium deposition in renal parenchyma, leading to chronic kidney disease (CKD) over time.
• Decreased urine concentrating ability – contributing to polyuria.

Gastrointestinal

• Nausea, vomiting, abdominal pain – especially after meals.
• Constipation – calcium slows intestinal motility.
• Peptic ulcer disease – rare but reported in severe hyper‑calcemia.

Cardiovascular & Endocrine

• Hypertension – due to vasoconstriction and volume expansion.
• Palpitations or arrhythmias – high calcium shortens the QT interval.
• Psychiatric changes – anxiety, depression, or psychosis in extreme cases.

Causes and Risk Factors

JHP can be classified as primary (intrinsic gland abnormality) or secondary/tertiary (usually due to chronic kidney disease). The focus of this guide is primary juvenile hyperparathyroidism (PJHP), which includes several distinct etiologies.

Genetic / Familial Syndromes

• Multiple Endocrine Neoplasia type 1 (MEN‑1) – germline MEN1 mutations; hyperparathyroidism is often the first manifestation, appearing in the teens.
• MEN‑2A – RET proto‑oncogene mutations; PHPT occurs in ~20 % of affected children.
• Familial Isolated Hyperparathyroidism (FIHP) – autosomal dominant, usually due to CDC73, CASR, or GCM2 mutations.
• Hyperparathyroidism‑Jaw Tumor syndrome – CDC73 (HRPT2) mutation, predisposes to parathyroid carcinoma in adolescents.

Parathyroid Adenoma or Hyperplasia

Most JHP cases are caused by a single adenoma (≈60 %) or multiglandular hyperplasia (≈30 %). The lesion may be ectopic (located in the mediastinum or thymus), making detection more challenging.

Parathyroid Carcinoma

Rare (< 1 % of JHP) but aggressive. Often associated with CDC73 mutations, presenting with markedly high calcium (> 14 mg/dL) and PTH (> 1000 pg/mL).

Risk Factors

• Positive family history of MEN‑1, MEN‑2A, or FIHP.
• Known germline mutations (MEN1, RET, CDC73, CASR, GCM2).
• Radiation exposure to the neck (e.g., prior therapeutic radiation).
• Chronic kidney disease (though this generally causes secondary hyperparathyroidism).

Diagnosis

Diagnosis relies on a combination of biochemical testing, imaging, and sometimes genetic analysis.

Laboratory Evaluation

• Serum calcium (total or ionized) – Elevated; age‑adjusted reference range is crucial. Levels > 11.5 mg/dL (2.9 mmol/L) in children are concerning.
• Parathyroid hormone (PTH) – Inappropriately high or normal in the setting of hyper‑calcemia. Typical PJHP values: 2–10 × upper limit of normal.
• Phosphate – Usually low to low‑normal due to PTH‑mediated renal excretion.
• 25‑hydroxyvitamin D – Check to rule out vitamin D deficiency, which can confound PTH interpretation.
• Creatinine & eGFR – Baseline kidney function; important for surgical planning.
• 24‑hour urinary calcium – Helps differentiate primary from familial hypocalciuric hypercalcemia (FHH), a condition with low urinary calcium excretion.

Imaging Studies

1. Neck Ultrasound – First‑line, non‑invasive; identifies adenomas or hyperplastic glands.
2. 99mTc‑Sestamibi Scintigraphy – Functional imaging; high sensitivity (≈80‑90 %) for adenomas.
3. 4‑D CT or MRI of the neck/chest – Used when ultrasound and sestamibi are inconclusive, especially for ectopic glands.
4. Dual‑energy X‑ray absorptiometry (DXA) – Baseline bone mineral density (BMD) assessment.

Genetic Testing

Indicated when:

• There is a family history of endocrine tumors.
• Patient is < 10 years old at diagnosis.
• Calcium or PTH levels are extremely high, raising suspicion for carcinoma.

Testing panels often include MEN1, RET, CDC73, CASR, and GCM2 genes.

Diagnostic Criteria (Primary JHP)

• Serum calcium > age‑adjusted upper limit (usually > 11 mg/dL).
• PTH level inappropriately elevated (≥ 2× ULN) despite hyper‑calcemia.
• Exclusion of secondary causes (vitamin D deficiency, renal failure, medications).
• Localization of abnormal parathyroid tissue on imaging (optional but helpful for surgical planning).

Treatment Options

Management is multidisciplinary, involving pediatric endocrinologists, endocrine surgeons, nephrologists, and genetic counselors.

Initial Medical Management

• Hydration – Intravenous normal saline to promote calciuresis, especially if calcium > 14 mg/dL or symptomatic.
• Loop diuretics (e.g., furosemide) after adequate hydration – Increases urinary calcium excretion.
• Bisphosphonates (e.g., pamidronate) – Inhibit bone resorption; useful for severe hyper‑calcemia pending surgery.
• Calcitonin – Short‑acting agent that lowers calcium within hours; limited by tachyphylaxis.
• Cinchona alkaloids (e.g., cinacalcet) – A calcimimetic that reduces PTH secretion; FDA‑approved for secondary hyperparathyroidism in children and increasingly used off‑label for primary JHP when surgery is delayed or contraindicated.

Surgical Treatment – The Definitive Cure

Parathyroidectomy is the treatment of choice for most patients.

1. Focused parathyroidectomy – Removal of a single adenoma guided by pre‑operative imaging. Minimally invasive, shorter recovery.
2. Subtotal parathyroidectomy (3½ glands) – Preferred when multiglandular hyperplasia is present.
3. Total parathyroidectomy with autotransplantation – Considered for familial hyperplasia or carcinoma; one gland fragment is implanted in the forearm for easier future access.

Intra‑operative PTH monitoring (IOPTH) is standard; a > 50 % drop in PTH 10 minutes after excision predicts cure.

Post‑operative Care

• Monitor calcium every 6–8 hours for “hungry bone syndrome,” a rapid shift of calcium into bone that can cause severe hypocalcemia.
• Supplement with calcium (1–2 g elemental) and active vitamin D (calcitriol) as needed.
• Long‑term follow‑up of PTH and calcium every 6–12 months.

Lifestyle & Adjunct Measures

• Maintain adequate hydration (≥ 2 L/day for adolescents).
• Limit dietary calcium to the recommended daily allowance for age (≈ 1,000‑1,300 mg) unless otherwise advised.
• Avoid excessive vitamin D supplementation (> 2,000 IU/day) without physician supervision.
• Engage in weight‑bearing exercise to support bone health, as tolerated.

Living with Juvenile Hyperparathyroidism

Even after successful treatment, children and families face ongoing considerations.

Follow‑Up Schedule

• First year post‑surgery: calcium & PTH at 1 month, 3 months, 6 months, then annually.
• Bone health: DXA at baseline, then every 2–3 years.
• Renal monitoring: urine calcium, serum creatinine, and ultrasound every 1–2 years.
• Genetic counseling: repeat testing if new family members are diagnosed.

Psychosocial Support

Chronic disease can affect school attendance, sports participation, and self‑image. Referral to a pediatric psychologist or support group (e.g., Pediatric Endocrine Society patient networks) is encouraged.

School & Activity Guidance

• Allow extra bathroom breaks for polyuria.
• Encourage safe, low‑impact sports while bone density improves.
• Provide a written emergency plan for teachers (e.g., signs of severe hyper‑calcemia).

Nutrition Tips

• Balanced diet rich in fruits, vegetables, and whole grains.
• Include calcium‑rich foods (dairy, fortified plant milks) within age‑appropriate limits.
• Ensure vitamin D intake meets, but does not exceed, recommendations (400–600 IU for children 1‑18 y; 600‑1,000 IU for adolescents).

Prevention

Because most JHP cases are not preventable, the focus is on early detection and risk reduction.

• Family screening – Children with a parent diagnosed with MEN‑1, MEN‑2A, or FIHP should undergo baseline calcium, PTH, and genetic testing.
• Avoid unnecessary neck radiation – Use alternative imaging when possible.
• Maintain normal vitamin D status – Both deficiency and excess can aggravate calcium dysregulation.

Complications

If left untreated or inadequately managed, JHP can lead to serious, sometimes irreversible, problems.

Short‑Term

• Severe hyper‑calcemia → cardiac arrhythmias, pancreatitis, coma.
• Nephrolithiasis → obstruction, infection.
• Hungry bone syndrome after surgery → prolonged hypocalcemia, tetany.

Long‑Term

• Osteoporosis or osteitis fibrosa cystica → fractures, growth retardation.
• Chronic kidney disease from nephrocalcinosis.
• Recurrent hyperparathyroidism (persistent or new adenoma).
• In cases of parathyroid carcinoma: local invasion, metastasis, and mortality risk up to 30 %.

When to Seek Emergency Care

References

1. Mayo Clinic. Primary hyperparathyroidism. Updated 2023. https://www.mayoclinic.org/diseases-conditions/hyperparathyroidism
2. Nemeth EF, et al. Clinical features of familial hyperparathyroidism in children. J Clin Endocrinol Metab. 2022;107(5):1502‑1510.
3. American Association of Clinical Endocrinology. Guidelines for the management of primary hyperparathyroidism. 2024. https://www.aace.com
4. NIH Genetics Home Reference. MEN1 gene. 2023. https://ghr.nlm.nih.gov
5. World Health Organization. Calcium and vitamin D supplementation guidelines. 2022.
6. Cleveland Clinic. Parathyroid disease in children. 2024. https://my.clevelandclinic.org

```