Enlargement (hyperplasia) of two or more parathyroid glands accounts for most other cases. A cancerous tumor is a very rare cause of primary hyperparathyroidism. One or more of the parathyroid glands produces high amounts of parathyroid hormone. This leads to high calcium levels and low phosphorus levels in your blood.

Your pituitary gland secretes two important hormones that work together to regulate processes in your reproductive system: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones are chemical messengers that signal your sex organs (ovaries or testes) to start processes needed to support your reproductive health.