Parathyroid

Phosphorous balance in chronic kidney disease

Phosphorous balance in chronic kidney disease

In the setting of chronic kidney disease, elevated blood phosphorous levels can increase the risk of death, in addition to cardiovascular, parathyroid and bone disorders. This case shows us that the other extreme is also dangerous: severe oral phosphorous restriction and severe hypophosphatemia lead to profound muscle weakness, ostemalacia, osteoporosis and multiple bone fractures. Arisotle's aurea mediocritas applies nicely here too.

GT

Mineral bone disorder in the setting of kidney disease.

Mineral bone disorder in the setting of kidney disease.

This is a nice summary of the latest guidelines on diagnosis and management of mineral bone disease induced by chronic kidney disease. Kidney anomaly can be classified functionally via estimated GFR or structurally via proteinuria.

Guidelines emphasize the need for bone density scan, bone biopsy, parathyroid hormone, calcium and phosphorus measures in the right context. Vitamin D analogs and phosphate binders are also discussed. See below for detailed recommendations.

GT

A simultaneous occurrence of primary hyperparathyroidism and amyloidosis 

A simultaneous occurrence of primary hyperparathyroidism and amyloidosis 

This is an interesting case where identification and treatment of primary hyperparathyroidism led to early diagnosis and management of IgA MGUS systemic amyloidosis. Other similar cases have been reported in the literature. More research would be needed however to clarify the relationship between primary hyperparathyroidism and primary amyloidosis; whether it is coincidental, associative or causative. 

GT

Recombinant PTH for Chronic Primary Hypoparathyroidism

Recombinant PTH for Chronic Primary Hypoparathyroidism

Primary hypoparathyroidism (PHPT) is a rare endocrine condition defined by hypocalcemia and deficient parathyroid hormone (PTH). It is primarily managed with high dose oral calcium and vitamin D supplementation instead of targeting the root cause of deficient PTH.

Conventional treatment is difficult to manage and often inadequate at controlling symptoms and preventing complications. RhPTH (1-84) is a recombinant form of PTH that acts as a direct substitute to the native hormone. It is a novel therapy that allows significant dose reductions in calcium and vitamin D supplementation, while achieving improved serum calcium, phosphate and calcium-phosphate product levels.

These biochemical advantages over the conventional therapy can translate to significant clinical benefits: reduced adverse events and improved quality of life. Our patient experienced just that with PTH replacement therapy. We propose a simple and practical protocol of how to initiate and titrate PHPT treatment. We emphasize the need for RhPTH(1-84) in all patients with resistant or refractory hypoparathyroidism.

EZ,  IB,  GT

Primary hyperparathyroidism: how not to miss parathyroid tumors

Primary hyperparathyroidism: how not to miss parathyroid tumors

The 4-dimensional CT scan (4dCT) is very useful in localizing parathyroid tumors prior to surgery. However its true precision is unknown. Parathyroid masses can produce excessive PTH leading to hypercalcemia, hypophosphatemia, osteoporosis, kidney stones and vascular calcifications. Appropriate identification and resection of adenomas is thus imperative.

Study discovers that 4dCT is inaccurate in about 30% of the cases, primarily due to the following clinical and anatomical reasons: presence of multiglandular hyperparathyroidism (or 7.6), an inferiorly located parathyroid adenoma (or 6.8), a small parathyroid mass <1.0 cm (or 4.4), and existence of confounding thyroid nodules (or 1.8).

These findings would be important to an endocrine surgeon performing parathyroidectomies, as it changes intraoperative expectations and intervention.

GT

Vitamin D alternative

Vitamin D alternative

A nice case showing superiority of calcifediol daily over cholecalciferol weekly in supplementing vitamin D levels and improving hypocalcemia, hyperparathyroidism and bone mineralization in someone with malabsorptive bariatric surgery (biliopancreatic diversion).

Chronic malabsorption can cause malnutrition, leading to poor liver function and reduced ability to hydroxylate vitamin D3 to D3-25OH, subsequently inducing calcium metabolic derangements and lower bone density.

Calcifediol – a preformed D3-25OH and an easier absorbed (due to an extra hydroxy group) form of vitamin D – bypasses the need for hepatic conversion of D3 to D3-25, and helped the index patient achieve impressive outcomes in 2-6 months.

Findings suggest using calcifediol in persons with refractory hypovitaminosis D and hypocalcemia in the setting of advanced gastrointestinal malabsorption.

GT

Decreased Parathyroid Hormone, Activated Vitamin D and Serum Calcium

Decreased Parathyroid Hormone, Activated Vitamin D and Serum Calcium

Parathyroid hormone (PTH) is responsible for calcium release from the bone and activation of vitamin D in the kidney. Activated vitamin D, called D1/25, in turn stimulates GI track for proper calcium absorption. Reduced quantity or quality of PTH can lead to hypocalcemia.

This original retrospective study from University of Maryland shows that supplementation with pre-hormone vitamin D2 (high dose) protects the patient from hypocalcemia more than activated-hormone Calcitriol, without causing hypercalcemia, renal injury or kidney stones.

It is important to note that study subjects must have had partial PTH deficiency in order to respond to D2 better than Calcitriol; or perhaps, D2 is converted to D1/25 via other non-PTH-dependent pathways.

GT

2016 Guidelines: Primary Hyperparathyroidism

2016 Guidelines: Primary Hyperparathyroidism

Primary hyperparathyroidism is a common disorder that arises from autonomous overproduction of parathyroid hormone by abnormal parathyroid glands. The disease is characterized by the persistent elevation of total serum calcium levels with corresponding elevated or inappropriately normal PTH levels.

The diagnosis of pHPT is biochemical. The clinical presentation is heterogeneous, and the associated symptoms overlap with those of aging and disease. Patients with symptomatic pHPT have overt signs and symptoms; however, the definition of symptomatic disease is still evolving. Patients with asymptomatic pHPT have no disease-specific symptoms.

Normocalcemic pHPT is a recently recognized, incompletely characterized variant that presents with high PTH levels and normal total and ionized serum calcium levels. Some, but not all, patients may progress over time to hypercalcemic pHPT.

JAMA

New FDA approval: parsabiv for hyperparathyroidism

New FDA approval: parsabiv for hyperparathyroidism

In February 2017, FDA approved Parsabiv intravenous infusion for treatment of hyperparathyroidism in patients undergoing hemodialysis.

End stage kidney disease can cause severe PTH rise, leading to worsening of hyperphosphatemia, higher bone turnover (ex, osteitis fibrosa cystica) and eventually renal osteodystrophy. Secondary kidney-related hyperparathyroidism can increase mortality and morbidity in affected patients.

Parsabiv is supposed to break the cycle of hyperphosphatemia by augmenting the action of calcium thus reducing secretion of PTH by parathyroid chief cells. Results are impressive.

GT