Table 2.

Non-Classical Manifestations of NHPT and Their Putative Mechanisms

	Explanation
Hypertension	PTH1R receptors on vascular cells may increase vascular tone, and, therefore resistance, leading to increased arterial blood pressure.
Aldosterone excess	PTH levels correlate with aldosterone levels, with direct PTH stimulation of the adrenal glands.
Cardiovascular morbidity	Increased PTH levels have been associated with cardiovascular comorbidities. However, parathyroidectomy has not yet been shown to reduce cardiovascular comorbidity.
Hyperglycemia	Increased PTH levels have been associated with insulin resistance and hyperglycemia. Parathyroidectomy has not yet been shown to improve HbA1c, but may improve blood glucose levels.
Quality of life (QoL)	Quality of life may be reduced in NHPT. Serum calcium levels may directly affect QoL, because surgery improves a number of domains of QoL if patients have preexisting mild hypercalcemia due to PHPT, compared to patients with normal serum calcium due to NHPT.
Muscle function	Muscle strength and function are impaired in patients with NHPT compared to healthy controls.
Immune function and gut microbiota	Immune function and gut microbiota may play a role in PHPT and NHPT as they may affect the severity of bone complications. This requires further investigation.

NHPT, normocalcemic primary hyperparathyroidism; PTH1R, parathyroid hormone 1 receptor; PTH, parathyroid hormone; HbA1c, glycated hemoglobin; PHPT, primary hyperparathyroidism.