The influence of parathyroid hormone and its fragments on results from midregion and C-terminal specific radioimmunoassays

Indications for parathyroidectomy and extent of treatment for patients with secondary hyperparathyroidism

Some manifestations of secondary hyperparathyroidism affect most if not all patients with chronic renal failure and can affect many different organ systems. Proper medical treatment is essential and should be attempted before considering surgical intervention. The symptoms that most often resolve after parathyroidectomy include bone pain and intractable pruritus. Other useful indications for operation include a marked elevation of the parathyroid hormone level and the elevation of the calcium x phosphate product over 70. Both subtotal parathyroidectomy and total parathyroidectomy with autotransplantation have been advocated as the best operative approach. Each of these procedures has its own advantages and disadvantages which should be considered for each individual case. Localizing procedures should be reserved for patients with persistent or recurrent hyperparathyroidism, as diffuse parathyroid hyperplasia is the most common operative finding in secondary hyperparathyroidism.

Immunological evidences for the presence of small late carboxylterminal fragment(s) of human parathyroid hormone (PTH) in circulation in man

Two antisera, C-52 and C-97, raised against bovine (b)PTH(1-84) in guinea pigs, were evaluated with 125I-[tyr53] human (h)PTH(53-84) as tracer and intact hPTH(1-84) and synthetic hPTH(39-84), representative of large carboxylterminal ("C") fragments found in circulation, as standards. In both assays, hPTH(39-84) was 5-6 times more potent than hPTH(1-84) on a molar basis in displacing the tracer. With both antisera, progressive deletion at the aminoterminal end of large "C" fragments, as in hPTH(53-84) and hPTH(65-84), lead to decreased immunoreactivity, hPTH(69-84) being non-immunoreactive. The mid-carboxylterminal fragments, hPTH(44-68) and hPTH(39-68), did not react in either assay. Each antiserum measured known quantities of pure hPTH(1-84) or hPTH(39-84) standards similarly. Serum PTH values obtained with antiserum C-97 were about 3 times higher in renal failure, 1.75 times higher in normal individuals and those with primary hyperparathyroidism, while similar to values measured with antiserum C-52 in individuals with secondary hyperparathyroidism without renal failure or with pseudohypoparathyroidism. When circulating PTH taken from patients with these disorders was fractionated by gel chromatography, both antisera recognized similar peaks of intact hPTH(1-84) and of large "C" fragments while antiserum C-97 further recognized a peak of smaller "C" fragments. This explained the different clinical behavior of the latter antiserum. Our findings demonstrate the existence of small late "C" fragments in circulation. They further suggest an influence of serum calcium and of renal function on the quantity of these fragments.