ABSTRACT
Serum Ca2+ exists in more than one form, yet about 50% is ionized (Part B). Ionized Ca2+ is the only form that influences secretion of PTH, and can be used for the maintenance of neuromuscular excitability and blood coagulation. Approximately 10% to 15% of serum calcium is complexed with phosphate, citrate, or bicarbonate, while 40% is protein bound to albumin and, to a much lesser extent, - and - globulins. Complexed and protein-bound forms are circulating storage forms from which Ca2+ can be readily released.
