The four, tiny, parathyroid glands are embedded in the posterior aspect of the thyroid gland (see Figure 6.10). Parathormone orparathyroid hormone (PTH) is secreted by the parathyroid glands. This hormone plays an important role in calcium metabolism.
The net effect of parathormone is to increase cal-cium levels in the blood by increasing absorption of calcium from the gut and the bones and reducing cal-cium excretion in the urine. An increase in bone re-sorption is a result of stimulating osteoclastic activity . Parathormone also stimulates vitamin D (another hormone that participates in calcium me-tabolism) formation in the kidney.