Immunohistological studies of nonthyroidal calcitonin-producing tumors

A series of oat cell carcinomas of the lung and some corresponding sputum specimens were studied along with other tumors by immunoperoxidase histology for the presence of calcitonin, beta-endorphin, and ACTH. Sixteen of 31 tissues were positive for calcitonin, 12 of 14 were positive for beta-endorphin, and 11 of 14 were positive for ACTH immunoreactivity. Many tissues contained all 3 peptides, and in some sections these peptide immunoreactivities appeared to be present in the same cells. These studies suggest that there is a releationship in oat cell carcinoma of the lung and other tumors among the 3 peptides, although the basis of this relationship is not clear.

Distribution of immunoreactive calcitonin in the rat pituitary gland

Immunohistochemical (immunoperoxidase) studies were performed on 478 sections from 97 rat pituitary glands with rabbit antisera to unconjugated human synthetic calcitonin beta-endorphin, and/or ACTH-(17--39). Calcitonin-positive cells were present in a majority of the anterior lobes studied, whereas they were present in only a minority of the intermediate lobes. Calcitonin-positive cells were also present in chronically thyroidectomized animals. Beta-Endorphin-positive cells were uniformly present in the intermediate lobes as were the ACTH-positive cells. In the anterior pituitary lobes, beta-endorphin-positive cells were more populous than the ACTH-positive cells, and in general, there was a dissociation of the cellular elements containing beta-endorphin, ACTH, and calcitonin. Although it remains possible that there is calcitonin-like immunoreactivity within a precursor molecule that is differentially processed by pituitary cells, these studies are more consistent with the view that immunoreactive calcitonin is present in pituitary cells which are not as yet precisely and consistently related to any identifiable population of hormone-producing cells.

Presence by radioimmunoassay of a calcitonin-like substance in porcine pituitary glands

We studied acidic acetone extracts of whole porcine pituitary glands for the presence of immunoreactive calcitonin (CT) using a porcine CT (pCT) RIA which did not react with other known pituitary hormones. Four preparations of porcine pituitary extract contained immunoreactive CT. Three of these displayed inhibition of binding parallel to that of authentic pCT in the pCT RIA and contained a single peak of immunoreactivity similar to pCT when studied by two different gel filtration chromatography systems. One preparation of porcine pituitary extract showed nonparallelism in RIA dose-dilution experiments and multiple immunoreactive species both similar to and larger than pCT on gel filtration in 6 M guanidine HCl. The effect of the reduction of disulfide bonds, followed by carboxymethylation of sulfhydryl groups, on immunoreactivity and apparent molecular size was similar for the CT-like substance in porcine pituitary extract and for authentic pCT. Preliminary immunohistological studies showed cytoplasmic staining in cells of the porcine adenohypophysis. These results demonstrate that the porcine pituitary gland contains a substance which has some of the immunochemical and biochemical properties of thyroidal pCT.

1,25-Dihydroxyvitamin D3 receptor-like macromolecule in rat osteogenic sarcoma cell lines

The hormonal metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), exerts its biological effects by initially binding to a cytosolic receptor protein. Such a protein has been demonstrated in the target organs of vitamin D3 including bone. Although the role of 1,25(OH)2D3 on the skeleton has been extensively studied in normal bone, nothing is known about its effects, if any, in abnormal bone growth. Rat osteogenic sarcoma is a useful model for bone malignancy. Tumor cells retain differentiated functions including the ability to form bone and to respond to parathyroid hormone, prostaglandins, and to a smaller extent to calcitonin with increases in cyclic AMP levels. We have here evaluated osteogenic sarcoma cell lines for the presence of a receptor for 1,25(OH)2D3. We have utilized sucrose gradient sedimentation, saturation analysis, and DNA-cellulose chromatography. Cytosol preparations from these cell lines contain a 3.3 S saturable macromolecule which binds 1,25(OH)2D3 with specificity and high affinity (Kd = 2 x 10(-10) M). The sterol-macromolecule complex binds to DNA-cellulose and its elution profile from this affinity resin is similar to that of the 1,25(OH)2D3 receptor from normal rat bone. These tumor cells should serve as a useful model for studying the action of 1,25(OH)2D3 in bone and the role of this metabolite in the biology of bone malignancy.

Radioiodine as an adjunct to the surgical treatment of medullary thyroid carcinoma

After total thyroidectomy for medullary thyroid carcinoma, a 50-yr-old male was found to have decreased but still abnormally elevated plasma calcitonin levels. A thyroid scan with 131I revealed remaining thyroid tissue primarily in the form of a thyroglossal duct remnant. Two courses of 131I treatment of 30 and 150 mCi, respectively, produced a gradual decrease in plasma calcitonin. This study demonstrates that carefully selected patients may benefit from the use of 131I treatment as an adjunct to surgery in medullary thyroid carcinoma.

Immunoreactive calcitonin in human cerebrospinal fluid

The cerebrospinal fluid (CSF) of 123 male subjects was studied by RIA for the presence of immunoreactive calcitonin (CT). The hormone could be detected in the CSF of 75% of 63 subjects at a mean (+/- SE) concentration of 11.1 +/- 1.3 pg/ml, with a range of less than 2 to 55 pg/ml. In 31 subjects, simultaneous measurements were made of CSF and plasma CT and there was not significant correlation between them. Column chromatography of a lyophilized pool of CSF from 60 of the subjects demonstrated that most of the CT immunoreactivity eluted with or after radioiodinated human CT. Our studies demonstrate the presence of immunoreactive CT in human CSF but do not provide any direct evidence regarding the source of the immunoreactivity.

Calcitonin secretion in congenital nongoitrous cretinism

Plasma calcitonin (CT) was measured in the basal state and/or during provocative tests of hormone secretion in 11 children with congenital non-goitrous cretinism (CNC), in 1 girl with a lingual thyroid, and in 11 normal children. Basal and stimulated CT concentrations were significantly lower in the patients with CNC than in the normal subjects. Mean basal CT (+/- SE) was 41 +/- 4 pg/ml in the normal children, 24 +/- 3 pg/ml in the children with CNC, and 20 +/- 2 pg/ml in the patient with the lingual thyroid. The mean incremental CT responses to calcium infusion were 7.0 +/- 2 pg/ml in the children with CNC, 6.0 pg/ml in the patient with the lingual thyroid, and 146 +/- 47 pg/ml in the normal children. The children with CNC also demonstrated a significant delay in the return of the total serum calcium to basal level after the calcium infusion. The mean incremental CT response after infusion of pentagastrin was 7.6 +/- 2 pg/ml in the children with CNC, 10.0 pg/ml in the child with the lingual thyroid, and 34.4 +/- 11 pg/ml in the normal children. These data indicate that CT deficiency is present in children with CNC and suggest that the deficiency is a consequence of the defective embryologic development of the thyroid gland.

Age-related changes of calcitonin secretion in females

Calcitonin secretion was studied in 50 normal females from 20--69 yr of age, with 10 subjects in each decade. Hormone measurements were made by RIA during response to a 10-min infusion of calcium (as the chloride salt) at 3 mg/kg BW. There was a progressive decrease of the calcium-stimulated plasma calcitonin with age. Linear regression analysis demonstrated a significant (P less than 0.05) negative correlation (r = 0.29) between calcitonin response and age. Postmenopausal females had a significantly (P less than 0.01) smaller calcitonin response than premenopausal females. The time of maximum calcitonin response progressively shifted from 10 min in the younger subjects to 20 min in the older subjects. These studies demonstrated that calcitonin secretion decreases with age in females. This decrease may play some role in the pathogenesis of the progressive loss of bone mass which occurs with aging in females.

Effect of the menstrual cycle on calcium-regulating hormones in the normal young woman

To examine the effect of estrogens on circulating levels of calcium-regulating hormones, total serum calcium, ionized calcium, inorganic phosphate, immunoreactive parathyroid hormone, calcitonin, 1,25-dihydroxyvitamin D, and estradiol (E2) levels were assayed on menstrual cycle days 3 and 13 in 12 healthy young women. Despite a 3-fold increase in serum E2 levels by midcycle, no differences in the other factors were observed. Furthermore, iv infusion of calcium (3 mg/kg over a 10-min period) produced similar changes in the serum levels of immunoreactive parathyroid hormone and calcitonin on days 3 and 13 in 8 women. Our findings suggest that in normal menstruating women, endogenous increases in E2 neither directly nor indirectly stimulate 1,25-dihydroxyvitamin D production, nor do they affect circulating levels of the hormones known to influence calcium homeostasis in man.

Relationship of fasting urinary calcium to circulating estrogen and body weight in postmenopausal women

Circulating estradiol (E2), estrone (E1), adrostenedione, and testosterone levels were measured in 40 normal postmenopausal women of widely varying body weights. The fasting urinary calcium to creatinine ratio (Ca:Cr) was also quantitated as an index of bone resorption. Significant positive correlations of E2 and E1 were found with body weight and correlations of E2 and E1 were found with body weight and percent ideal weight but not with height, age, or years since menopause. No correlations were observed between circulating androstenedione and testosterone levels and any of these characteristics. Significant negative correlations were noted between Ca:Cr and percent ideal weight and between Ca:Cr and E2 and E1 concentrations. Administration of 10 micrograms ethinyl E2 to 10 postmenopausal subjects for 30 days reduced Ca:Cr to the level observed in 20 premenopausal women. These data suggest that body weight can influence urinary calcium excretion. It is possible that the reduced amounts of endogenous estrogen found in conjunction with low body weight may be a factor contributing to the greater loss of urinary calcium and the more frequent occurrence of osteoporosis in slender postmenopausal women.

Reactivity of ACTH and synthetic ACTH peptides with antisera to human calcitonin

We studied reactivity of highly purified pituitary hormones in our human calcitonin (hCT) radioimmunoassay (RIA) which can detect 1 pg of hCT. ACTH at doses of greater than 1 microgram of peptide per RIA tube reacted in the hCT assay, as did beta-endorphin (beta EPH) at a dose of 10 micrograms per tube. No reactivity was observed with comparable concentrations of all other known pituitary hormones. ACTH also reacted at doses greater than 1 microgram per tube with 7 other hCT antisera which recognized differing antigenic determinants in the calcitonin molecule but it was not reactive with 2 antisera against porcine calcitonin or 2 antisera against salmon calcitonin. This slight degree of cross-reactivity of hACTH and beta EPH in the hCT RIA cannot account for the presence of immunoreactive CT in pituitary glands. Nevertheless, antisera used for the localization of peptides must be rigorously tested for the existence of cross-reactivities with other possible substances, especially if such antisera detect the peptide in unexpected tissues.

Calcitonin secretion in primary hyperparathyroidism

Plasma calcitonin (CT) was studied by RIA in 55 patients with surgically proven primary hyperparathyroidism. Basal hormone measurements were performed in all patients and provocative tests of CT secretion were performed in 7. Biochemical measurements were also made before and after parathyroidectomy in 34 patients. Plasma CT was significantly increased above normal in the male but not the female group of patients with primary hyperparathyroidism. A similar sex difference in plasma CT was also seen during provocative testing. In contrast to normal subjects, plasma CT was also significantly correlated to serum calcium concentration in the males but not the females. Hormone concentrations returned to normal after parathyroidectomy in the males and did not significantly change in the females. These studies demonstrate that some patients with primary hyperparathyroidism, especially males, may have an increase, perhaps compensatory, in plasma CT. As with normal females, females with primary hyperparathyroidism seem to have decreased CT reserve.

Acute and chronic fluctuations of immunoreactive and biologically active plasma calcitonin in the rat

Using a sensitive calcitonin (CT) immunoassay and a newly developed bioassay capable of detecting 0.025 MRC mU CT, we have studied acute and chronic plasma CT fluctuations in male and female rats. Immunoassay of serial plasma samples revealed progressive increases in plasma CT concentrations during aging; female rats have higher CT concentrations than age-matched males. Acute periodic CT fluctuations were discovered by immunoassay of plasmas obtained at 3-h intervals; the greatest values occurred just before and during feeding. Fed rats have higher CT than starved rats. We have used immunoadsorbent chromatography to concentrate specifically CT moieties from large volumes of plasma for concurrent immunoassay and bioassay measurements of circulating CT. These concurrent measurements of immunoextracted plasma CT demonstrate that for normal rats, our immunoassay measurements correspond to bioassay measurements. In 1-yr-old rats on a regulated feeding schedule, the biological (hypocalcemic) activity of CT recovered from 15 ml peripheral plasma ranged from less than 0.15 mU in starved males to 0.78 mU in feeding females. We conclude that biologically active CT circulates in normal rats and that the blood concentration of biologically active CT progressively increases during somatosexual maturation, being highest in old females, and increases acutely just before and during feeding.

Plasma parathyroid hormone and calcium are related to sleep stage cycles

To study dynamic interactions among parathyroid hormone (PTH), plasma calcium, and brain states, seven normal subjects were studied for a total of eight nights in our sleep laboratories. Plasma samples were obtained at 10- to 20-min intervals for PTH and calcium determinations. Electroencephalogram, eye movements, and muscle tone were recorded to determine sleep stages. On each night, several distinct peaks in PTH concentration were seen, which in some cases exceeded the all night mean PTH by as much as 300%. Peaks in plasma PTH were significantly nonrandom and tended to recur about every 100 min. PTH concentration was significantly related to cycles of stages 3 and 4 sleep. Total plasma calcium varied less but was significantly related to cycles of rapid eye movement sleep and to cycles of stage 2 sleep. PTH and calcium were significantly interrelated, especially at high frequencies above 40 cycles/day (1 cycle 36 min). In the 14.4 cycles/day (1 cycle/100 min) frequency range where most PTH and calcium variability was found, however, PTH and calcium were more closely related to sleep stages than to each other. These results suggest that the regulation of PTH and calcium is complex and may involve interactions with neural systems.

Demonstration by immunoperoxidase histochemistry of calcitonin in the anterior lobe of the rat pituitary

We have demonstrated by a specific immunoperoxidase procedure the presence of calcitonin-containing cells in the rat pituitary gland. These cells are widely distributed throughout the anterior lobe and seem to constitute the entire population of cells of the intermediate lobe. No such cells were seen in the posterior lobe. The presence of calcitonin-containing cells in the pituitary provides novel implications about the physiological significance of this hormone.

Assessment of acute and chronic changes in parathyroid hormone secretion by a radioimmunoassay with predominant specificity for the carboxy-terminal region of the molecule

A sensitive RIA for parathyroid hormone (PTH) with specificity for the carboxy-terminal region of the hormone was developed and applied to clinical studies. The assay was useful in identifying patients with chronic hyperparathyroid states, such as primary and secondary hyperparathyroidism. In addition, the assay could detect acute changes in PTH seen during calcium, pentagastrin, and EDTA infusions and after parathyroidectomy. These studies demonstrated that an immunoassay with predominant specificity for the carboxy-terminal fragment of PTH can be used to evaluate acute as well as chronic changes in hormone secretion.

ACTH-secreting medullary carcinoma of the thyroid presenting a severe idiopathic osteoporosis and senile purpura: report of a case and review of the literature

A 64-yr-old female presented with severe osteoporosis and easy bruisability of over 2-yr duration. Biopsy of a neck mass revealed medullary carcinoma of the thyroid. Subsequently, lymphangitic pulmonary metastases were demonstrated which had been present radiographically for at least 4 yr. Basal serum calcitonin was markedly elevated and increased during calcium infusion. The diagnosis of ectopic ACTH syndrome was first entertained when hypokalemic alkalosis was observed during evaluation of her carcinoma. Elevated urinary 17-hydroxycorticosteroids, 17-ketosteroids, plasma cortisol, and immunoreactive plasma ACTH levels were documented. Adrenal steroidogenesis seemed to suppress on high dose dexamethasone. The primary tumor and its metastases contained high concentrations of immunoreactive ACTH and beta-melanocyte-stimulating hormone. Hepatic metastases contained extremely high concentrations of calcitonin. In contrast to the usual presentation of the ectopic ACTH syndrome as primarily hypokalemic alkalosis and glucose intolerance, patients with relatively benign and indolent ACTH-secreting tumors, such as certain cases of medullary carcinoma of the thyroid, may present with more typical signs and symptoms of Cushing's syndrome. The more pronounced cushingoid features in this latter group presumably reflects a more prolonged period of exposure to elevated glucocorticoid levels. Ten cases of ACTH-secreting medullary carcinoma of the thyroid from the literature are discussed. Extopic ACTH production by such tumors should be considered in the evaluation of patients with Cushing's syndrome or unexplained severe osteopenia.

Calcitonin secretion in normal human subjects

A sensitive RIA for human calcitonin has been developed which can detect 1-2 pg hormone. This procedure permits the measurement of the low concentrations of calcitonin in the unextracted plasma of normal human subjects. In 55 normal adults, mean plasma calcitonin was 24 pg/ml with an SD of +/- 18 pg/ml, an SE of +/- 2 pg/ml, and a range of less than 10 - 75 pg/ml. There were no discernible age or sex differences in basal hormone concentration. Infusions of calcium, pentagastrin, and glucagon stimulated plasma calcitonin, whereas food and oral calcium did not. The stimulatory effect of pentagastrin was greater in males than in females. These data demonstrate that the low concentration of calcitonin in humans can be stimulated by several secretagogues and suggest that females may have decreased calcitonin reserve.