Hyperparathyroidism Causes and Management

Primary Hyperparathyroidism

• Primary hyperparathyroidism is defined by hypercalcemia with elevated or inappropriately normal PTH levels, most commonly caused by adenoma or hyperplasia of one or more parathyroid glands, leading to calcium removal from bones and increasing osteoporosis risk 1
• The American College of Endocrinology recommends that primary hyperparathyroidism be treated with parathyroidectomy in symptomatic patients, with the goal of reducing the risk of osteoporosis and kidney stone formation 1

Secondary Hyperparathyroidism

• The National Kidney Foundation states that chronic kidney disease (CKD) is the most common cause of secondary hyperparathyroidism, with nearly all patients developing parathyroid gland hyperplasia as kidney function declines 2
• Phosphate retention occurs early in CKD and is the fundamental initiating factor, triggering the cascade even before hyperphosphatemia develops, with high phosphate intake directly provoking secondary hyperparathyroidism in early CKD stages 3
• Decreased 1,25-dihydroxyvitamin D production results from failing kidneys, reducing intestinal calcium absorption and causing hypocalcemia, with the Endocrine Society recommending vitamin D supplementation in CKD patients 4, 2
• PTH levels begin rising when GFR falls below 60 mL/min/1.73 m², with the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommending regular monitoring of PTH levels in CKD patients 5

Vitamin D Deficiency

• Vitamin D insufficiency is extremely prevalent in CKD patients, leading to reduced intestinal calcium absorption, hypocalcemia, and compensatory PTH elevation, with the National Kidney Foundation recommending vitamin D supplementation in CKD patients 2
• PTH reference values are 20% lower when established in vitamin D-replete individuals compared to those with unknown vitamin D status, with the Endocrine Society recommending vitamin D measurement in patients with secondary hyperparathyroidism 1

Post-Bariatric Surgery

• Patients who have undergone bariatric surgery may develop secondary hyperparathyroidism due to impaired calcium and vitamin D absorption, with the American Association of Clinical Endocrinologists recommending regular monitoring of calcium and vitamin D levels in post-bariatric surgery patients 6, 4

Tertiary Hyperparathyroidism

• Tertiary hyperparathyroidism results from long-standing, severe secondary hyperparathyroidism that has become autonomous, with approximately 10% of dialysis patients requiring parathyroidectomy after 10 years, increasing to 30% after more than 20 years, according to the National Kidney Foundation 2

Physiological and Demographic Factors

• PTH is higher in Black individuals compared to White individuals, with the Endocrine Society recommending consideration of racial differences in PTH interpretation 1
• PTH increases with age, possibly due to steady decline in GFR, leading to higher concentrations in people over 60 years old, with the American Geriatrics Society recommending regular monitoring of PTH levels in older adults 1
• PTH correlates positively with body mass index, with higher levels in obese patients, according to the Obesity Society 1

Pre-Analytical and Assay-Related Factors

• PTH measurement can be influenced by biotin supplements, which may cause underestimation or overestimation depending on assay design, with the Endocrine Society recommending avoidance of biotin supplements before PTH measurement 1
• Different PTH assay generations measure overlapping but distinct molecular forms, with second-generation assays overestimating biologically active PTH by detecting inactive fragments, according to the National Kidney Foundation 5

Critical Pitfalls to Avoid

• The National Kidney Foundation recommends not focusing solely on PTH levels without evaluating calcium, phosphorus, and vitamin D status, as this can lead to misdiagnosis 2
• Overlooking vitamin D insufficiency is a common error that perpetuates secondary hyperparathyroidism, with the Endocrine Society recommending regular measurement of vitamin D levels in patients with secondary hyperparathyroidism 2
• Attempting to maintain PTH in the "normal" range in CKD patients can cause adynamic bone disease, with the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommending stage-specific targets for PTH management in CKD patients 5
• Normal or low PTH in ESRD may indicate adynamic bone disease, which is also problematic and requires different management, according to the National Kidney Foundation 3

Etiology and Epidemiology of Primary Hyperparathyroidism

Prevalence of Underlying Causes

• A solitary parathyroid adenoma is responsible for roughly 80 % of primary hyperparathyroidism cases, representing the predominant cause of elevated PTH with hypercalcemia. 7

Multigland Disease

• Multiple adenomas or parathyroid hyperplasia account for 15–20 % of patients, indicating a multiglandular form of the disorder. 7

Malignant Etiology

• Parathyroid carcinoma is an uncommon entity, occurring in less than 1 % of primary hyperparathyroidism cases. 7

Hereditary Syndromes

• Hereditary conditions such as multiple endocrine neoplasia type 1 (MEN 1), MEN 2A, and familial isolated hyperparathyroidism should be considered in younger individuals or those with a relevant family history. 7