In PHP Type 1B, the pattern of serum calcium, phosphate, and PTH is:

In PHP Type 1B, the pattern of serum calcium, phosphate, and PTH is:

• A. Hypocalcemia, Hyperphosphatemia, High PTH
• B. Hypercalcemia, Hypophosphatemia, Normal PTH
• C. Hypocalcemia, Hypophosphatemia, Low PTH
• D. Normal calcium, Normal phosphate, Normal PTH

Answer: (A)

Pseudohypoparathyroidism type 1B involves resistance to parathyroid hormone at the tissues that normally respond to it. Because the kidneys and bones don’t respond to PTH, calcium cannot be raised effectively and phosphate isn’t excreted as it should be. In response to the resulting low calcium, the parathyroid glands secrete more PTH, but the target organs remain resistant. The net lab pattern is low serum calcium, high serum phosphate, and elevated PTH. This combination specifically reflects PTH resistance rather than a deficiency or excess acting on normally responsive tissues.

Pseudohypoparathyroidism type 1B involves resistance to parathyroid hormone at the tissues that normally respond to it. Because the kidneys and bones don’t respond to PTH, calcium cannot be raised effectively and phosphate isn’t excreted as it should be. In response to the resulting low calcium, the parathyroid glands secrete more PTH, but the target organs remain resistant. The net lab pattern is low serum calcium, high serum phosphate, and elevated PTH. This combination specifically reflects PTH resistance rather than a deficiency or excess acting on normally responsive tissues.