Pathophysiology of acromegaly.

This review discusses the pathophysiology of acromegaly. Acromegaly has been classified in this paper into distinct entities based on etiology, ultrastructural features of the pituitary, and cytogenesis. This classification has been proposed based on clinical signs, immunoperoxidase techniques, transmission electromicroscopy and immunoelectron microscopy. Pituitary causes of acromegaly include densely granulated adenomas, sparsely granulated adenomas, mixed growth hormone and prolactin cell adenomas, acidophil stem cell adenomas, mammosomatotroph cell adenomas, and pleurihormonal adenomas. GH cell hyperplasia and GH cell carcinoma are also discussed. Extrapituitary causes of acromegaly include eutopic GH cell adenoma in the sphenoid sinus or parapharyngeal region and excess GHRF secretion which may be eutopic or ectopic. The pathological, clinical, and biochemical evidence in favor of a pituitary or hypothalamic etiology of acromegaly has been reviewed. Finally, a multistage theory of GH cell tumorigenesis has been proposed as a model in an attempt to unify the genetic, environmental and biochemical factors implicated in the pathogenesis of acromegaly.

Induction of sodium iodide symporter gene and molecular characterisation of HNF3 beta/FoxA2, TTF-1 and C/EBP beta in thyroid carcinoma cells.

Thyroid carcinoma cells often do not express thyroid-specific genes including sodium iodide symporter (NIS), thyroperoxidase (TPO), thyroglobulin (TG), and thyrotropin-stimulating hormone receptor (TSHR). Treatment of thyroid carcinoma cells (four papillary and two anaplastic cell lines) with histone deacetylase inhibitors (SAHA or VPA) modestly induced the expression of the NIS gene. The promoter regions of the thyroid-specific genes contained binding sites for hepatocyte nuclear factor 3 beta (HNF3 beta)/forkhead box A2 (FoxA2), thyroid transcription factor 1 (TTF-1), and CCAAT/enhancer binding protein (C/EBP beta). Quantitative reverse transcription-polymerase chain reaction (RT-PCR) showed decreased expression of HNF3 beta/FoxA2 and TTF-1 mRNA in papillary thyroid carcinoma cell lines, when compared with normal thyroid cells. Forced expression of these genes in papillary thyroid carcinoma cells inhibited their growth. Furthermore, the CpG island in the promoter region of HNF3 beta/FoxA2 was aberrantly methylated; and treatment with 5-aza-2-deoxycytidine (5-Az) induced its expression. Immunohistochemical staining showed that C/EBP beta was localised in the nucleus in normal thyroid cells but was detected in the cytoplasm in papillary thyroid carcinoma cells. Subcellular fractionation of papillary thyroid carcinoma cell lines also demonstrated high levels of expression of C/EBP beta in the cytoplasm, suggesting that a large proportion of C/EBP beta protein is inappropriately localised in the cytoplasm. In summary, these findings reveal novel abnormalities in thyroid carcinoma cells.

Testosterone patches in the management of patients with mild/moderate systemic lupus erythematosus.

OBJECTIVES: Androgen deficiency has been associated with the development of systemic lupus erythematosus (SLE). The aim of this study was to test the efficacy of testosterone patches vs placebo in female SLE patients with baseline mild-to-moderate disease activity in a randomized, double-blind, single-centre placebo-controlled trial. METHODS: Patients received testosterone (150 microg) or placebo transdermal patches for 12 weeks. Patients were assessed at 4-weekly intervals for disease activity using the Safety of Oestrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index (SELENA-SLEDAI), Systemic Lupus Activity Measure-Revised (SLAM-R) and The British Isles Lupus Assessment Group (BILAG) indices, physician global assessment (PGA), quality of life using the SF-36 survey and sexual functioning using the Derogatis score. Data were analysed using two sample t-tests to compare the mean difference from baseline to week 12 in the testosterone patch and placebo groups. RESULTS: Thirty-four patients were recruited in to each group. There was no significant baseline difference between the groups in age, race or marital status. There was no significant difference between treatment groups in the mean change in SELENA-SLEDAI (0.547 +/- 3.72, P > 0.60), nor in PGA or BILAG system scores. The mean change in SLAM-R score was statistically different (2.06, S.D. 3.3, P = 0.01) but was not considered clinically meaningful. Health transition also showed a small change (P < 0.03). There was no significant difference in the Derogatis scores or toxicity. CONCLUSIONS: Testosterone patches were safe but did not significantly affect disease activity, quality of life or sexual functioning. Increased use of steroids in the placebo group may have confounded the study results.

Decidua produces a protein that inhibits choriogonadotrophin release from human trophoblasts.

To test the hypothesis that uterine decidua may modulate trophoblast function, trophoblasts and decidual cells were isolated from term placentas by enzymatic digestion and Percoll gradient centrifugation. Placental trophoblasts were cocultured with decidual cells and trophoblasts or JEG-3 choriocarcinoma cells were incubated with medium conditioned by decidual cells (DCM) for 72-96 h. In cocultures decidual cells inhibited choriogonadotropin (hCG) release from trophoblasts by 75% in comparison with controls (P less than 0.001). The DCM contained a factor that markedly inhibited hCG release from trophoblasts and JEG cells in vitro compared with controls. The inhibitory effect of the factor on hCG release was dose dependent, and could be eliminated by boiling the DCM for 30 min or proteolytic enzyme treatment. Ultrafiltration and Sephadex G-50 fractionation of the DCM indicated that the apparent molecular mass was 7,000-10,000 D. DCM also inhibited the stimulatory effect of exogenous cAMP on hCG secretion by JEG-3 cells, suggesting that DCM may interfere with activation of the cAMP-dependent protein kinases or transcription of hCG genes. These results suggest that the release of trophoblast hCG is under local paracrine control, regulated in part by a protein released by decidual cells.

Kinetics of growth and ectopic production of human chorionic gonadotropin by an ovarian cystadenocarcinoma cell line maintained in vitro.

An established ovarian papillary cystadenocarcinoma cell line, designated 163, released immunoreactive human chorionic gonadotropin (HCG) in vitro into the culture medium. The maximal rate of this ectopic activity (10 to 15 ng/day/10(6) cells) occurred at the onset of the logarithmic phase of cell growth and greatly exceeded the intracellular HCG content of cells approaching confluency (0.037 ng/10(6) cells). The HCG production was not detected during the plateau phase of growth. The rate of cellular proliferation and HCG release depended upon the frequency of media change in a manner suggesting that the two processes are interrelated and may be affected by such environmental factors as cell density, nutrient availability, and the accumulation of waste products. The addition of purified HCG to the cultures had no appreciable effect on either the cell growth or the accumulation of HCG. The release of HCG into the medium was greatly stimulated in the presence of sodium butyrate at concentrations from 1 to 10 mM, despite the fact that these concentrations of butyrate resulted in a marked decrease in the cell number/culture in comparison with control media. Equivalent amounts of sodium acetate had no effect on either cell growth or the release of HCG.

Clinical, biochemical, and pathologic features of radiation-associated hyperparathyroidism.

The clinical, biochemical, and pathologic findings in 43 patients with primary hyperparathyroidism (HPT) and a history of irradiation to the head or neck were compared with those found in a group of 162 patients with HPT without prior irradiation. There were no differences between the groups with regard to mean age at the time of diagnosis, male to female ratio, serum calcium, phosphorus, and parathyroid hormone concentrations; in the frequency of single parathyroid adenomas v multiglandular disease; or in associated nonthyroidal neoplasms. Asymptomatic HPT was found with greater frequency in the irradiated patients. Almost 80% of the patients with a history of irradiation had concomitant thyroid disease, primarily adenomas and carcinomas, while less than 50% of the patients without a history of irradiation had thyroid disease, mainly colloid nodules, at surgery.

Thyroid incidentalomas. Prevalence by palpation and ultrasonography.

BACKGROUND: Thyroid nodules are commonly identified on autopsy examination. There are relatively few descriptions, however, of the frequency with which thyroid nodules are encountered incidentally during the course of other investigations. METHOD: Prospective study to examine the prevalence of thyroid nodules in asymptomatic North American subjects, with palpation findings compared with findings on high-resolution ultrasonography. RESULTS: Palpable nodules were identified in 21 (21%) of 100 subjects, with nine solitary nodules (9%) and 12 multiple nodules (12%). In comparison, only 33 subjects were found to be free of any nodules by ultrasonography. Of the 67 subjects with abnormal ultrasound findings, 22 had solitary nodules (22%) and 45 had multiple nodules (45%). The prevalence of nodules was greater in women (72%) than in men (41%) (P < .02). A concordance rate of 49% was noted between ultrasound and findings by palpation. CONCLUSIONS: The data indicate that thyroid abnormalities are very common incidental findings, emphasizing the need for a conservative approach when such lesions are encountered incidentally.

Aromatase and gynecomastia.

An imbalance between estrogen action relative to androgen action at the breast tissue level results in gynecomastia. Enhancement of aromatization of androgens to estrogens is important in the pathogenesis of gynecomastia associated with obesity, aging, puberty, liver disease, thyrotoxicosis, 17-oxosteroid reductase deficiency. Klinefelter's syndrome, and neoplasms of the testes, adrenals and liver. A primary aromatase excess syndrome with exuberant gynecomastia had been found both sporadically and in a familial setting. Although aromatase inhibition would appear to be an important class of drugs to treat gynecomastia, relatively little published data with these drugs exist and most concern the use of delta1-testolactone, which reduces the size of the breast glandular tissue, but does not completely ameliorate the problem. Studies with the newer generation of more potent aromatase inhibitors need to be carried out.

Insulin stimulates synthesis and release of human chorionic gonadotropin by choriocarcinoma cell lines.

Recent studies have shown that insulin regulates placental lactogen, progesterone, and estrogen production from human trophoblast cells. This study was performed to examine whether insulin also regulates the production of hCG by this type of cell. After 24-36 h of preincubation, JEG-3 and JAR cells (2-3 x 10(5) cells/ml.well) or human term trophoblast cells (1 x 10(6) cells/ml.well) were exposed to the test hormone in serum-free Dulbecco's Modified Eagle's Medium for 24-96 h. Secretion of hCG from JEG-3 cells was stimulated by human insulin, human proinsulin, or porcine insulin in a dose-dependent manner, with lowest effective doses of 6.7, 96, and 53 mg/L, respectively. Time-course studies showed that hCG secretion peaked at 72-96 h with insulin exposure; in contrast, no decernable peak was seen without insulin in serum-free media. Exposure of JEG-3 cells for 24 h to 209 mg/liter insulin stimulated hCG synthesis, with 40 +/- 3% more immunoreactive intracellular hCG (P less than 0.05). Cells grown in the presence of insulin and [35S]methionine had 47 +/- 21% more labeled intracellular hCG and 56 +/- 13% more immunoprecipitable [35S]methionine-hCG secreted into the medium than the control cultures (P less than 0.05). During this time period, human placental lactogen release and total trichloroacetice acid-precipitable [35S]methionine protein were not increased. The insulin-induced stimulation of hCG synthesis was inhibited by cycloheximide. Additionally, insulin did not significantly affect total intracellular protein during 24-96 h of incubation. Insulin also increased hCG release from JAR cells, but not from human term trophoblast cells. A mouse monoclonal antibody to the IGF-I receptor inhibited the stimulation of insulin in JEG-3 cells. We conclude that insulin stimulates the synthesis and secretion of hCG from JEG-3 cells and JAR cells, and that hCG regulation in choriocarcinoma cells differs from that in primary human placental trophoblast cells. The effect of insulin on JEG-3 cells may be mediated in part through the insulin-like growth factor-I receptor.

Retinoic acid stimulates placental hormone secretion by choriocarcinoma cell lines in vitro.

Retinoic acid (RA), an active metabolite of vitamin A, is an important mediator of cellular differentiation and has been shown to stimulate human CG (hCG) secretion by JEG-3 choriocarcinoma cells in vitro. In order to determine whether RA stimulates the hCG secretion by other trophoblastic cell lines, we evaluated the effect of RA on hCG, hCG-alpha subunit (hCG-alpha), and progesterone secretion in three choriocarcinoma cell lines: JEG-3, JAR, and BeWo. RA stimulated hCG and hCG-alpha secretion in a dose-dependent fashion by each of the three cell lines. The time required to give a statistically significant increment of hCG and hCG-alpha over control cells was 48 h. The addition RA to cholera toxin (10 micrograms/ml) resulted in an additive or synergistic stimulation of hCG and hCG-alpha secretion by the three cell lines. Cycloheximide (1 microM) abolished the effect of RA on hCG and hCG-alpha secretion in the BeWo cell line. Progesterone secretion in response to RA was inconsistent. Progesterone secretion by both JEG-3 and BeWo cell lines were stimulated at high concentrations of RA (1 x 10(-6], whereas progesterone secretion by JAR cells was not stimulated. Intracellular levels of cAMP were not affected by RA treatment in the JEG and JAR cells. In the dosages used, RA did not significantly alter cell number in any of the cell lines. RA in physiologic concentrations stimulates hCG and hCG-alpha secretion by three choriocarcinoma cell lines in vitro. Whether RA is a physiologic mediator of placental hormone production is unknown.

Somatostatin analog induces insulin-like growth factor binding protein-1 (IGFBP-1) expression in human hepatoma cells.

As the somatostatin analog octreotide suppresses pituitary GH secretion and circulating IGF-1 levels, we examined its effects on human hepatoma (hep G2) cells which selectively express IGFBP-1. Octreotide (60 nM) stimulated IGFBP-1 up to 4.1-fold (p < 0.001 after 24 hrs). Induction of IGFBP-1 was first detectable after 12 hrs of 6 nM octreotide (1.5-fold, p < 0.03), and was confirmed by ligand blotting. Cholera toxin and forskolin induced IGFBP-1 independently and were also additive with octreotide. IGFBP-1 mRNA expression was induced 2.7-fold by octreotide. Thus, octreotide induces basal and stimulated IGFBP-1 in hepatocytes independently of insulin and GH. As IGFBP-1 may regulate peripheral IGF-1 action, induction of IGFBP-1 represents a novel pituitary-independent mechanism for octreotide action.

Pregnancy-specific beta 1-glycoprotein concentrations throughout pregnancy in the rhesus monkey.

Proteins that are immunologically related to human pregnancy-specific beta 1-glycoprotein (hSP1) have been detected in serum samples from pregnant subhuman primates. However, little information is available concerning the concentrations or secretory dynamics of SP1 in nonhuman primate pregnancy. To examine serum SP1 concentrations throughout rhesus monkey gestation, a heterologous RIA for rhesus SP1 (rSP1) was developed which used an antiserum against rSP1 and purified human SP1 as the standard and for iodination. No rSP1 was detected in serum samples from 8 normal male monkeys, 8 castrated females, or 10 regularly cycling females. Levels of rSP1 were measured in 260 serum samples from 43 pregnant monkeys. rSP1 was first detected on day 14 after mating, and all monkeys sampled 25 or more days after mating had detectable serum rSP1 levels. Serum rSP1 rose exponentially from day 14 to about day 50, followed by a more gradual rise until term. This pattern of secretion was in marked contrast to that found for macaque CG, which was already detectable 10 days after mating, peaked at 20 days, and returned to nonpregnant levels by day 40. The disappearance of rSP1 after delivery was best fit by a 2-component 4-parameter model with a mean residence time of 48 h. These data indicate that the pattern of rSP1 secretion throughout pregnancy is qualitatively similar to that found for hSP1, as is the long half-life of the protein in the circulation after delivery. rSP1 measurements may provide a useful index of placental function during rhesus pregnancy and serve as a model to study the biological role of SP1 in primates.

Beta-core fragment is a major form of immunoreactive urinary chorionic gonadotropin in human pregnancy.

A small mol wt fragment of the beta-subunit of hCG (beta-core fragment) is present in the urine, but not the serum, of pregnant women. We evaluated the relative proportions of this immunoreactive, but biologically inactive, fragment in urine from 15 women at different stages of pregnancy. Freshly voided urine was ultrafiltered and concentrated, and the molecular species of immunoreactive hCG were separated by Sephadex G-100 column chromatography. All urine samples contained the beta-core fragment, which eluted after the alpha-subunit of hCG. This fragment lacked the carboxy-terminal epitope of hCG, was inactive as an in vitro bioassay, and adsorbed to Concanavalin-A. The beta-core fragment was a major form the immunoreactive hCG in urine throughout pregnancy and accounted for over 90% of the immunoreactive hCG in urine from midpregnancy. The excretion pattern of the beta-core fragment can account for the low biological to immunological ratio of urinary hCG that occurs at different stages of pregnancy.

Comparison of serum pituitary thyrotropin and chorionic gonadotropin concentrations throughout pregnancy.

Concentrations of human pituitary thyrotropin (hTSH) and human chorionic gonadotropin (hCG) were measured by specific radioimmunoassays in serum samples obtained from 243 pregnant women. The hTSH levels demonstrated suppression during the sceond through the fourth months, followed by a linear rise to non-pregnant control levels throughout the remainder of gestation. At the time that the hCG levels were at their lowest concentration. However, a reciprocal relationship between the hCG and hTSH concentrations in individual samples was not found. The inverse relationship between mean levels of hTSH and hCG during early pregnancy suggest that the intrinsic thyroid-stimulating activity of hCG may be important in the control of thyroid function during the first trimester. The failure to confirm this relationship in individual serum samples indicates that other factors also influence maternal thyroid homeostasis during early gestation.

Human chorionic gonadotropin stimulates proliferation of Nb 2 rat lymphoma cells.

The effects of an onco-fetal hormone, hCG, were tested on replication of Nb 2 node rat lymphoma cells, which have previously been shown to be responsive to lactogenic hormone stimulation. Cells were maintained in suspension culture in Ham's F-10 medium containing horse serum (15%) and fetal calf serum (2.5%). Forty-eight hours before experiments, medium was replaced with horse serum (10%) only. In the absence of added hCG, cell doubling time was about 24 h. Purified hCG preparations (CR 119) and the Second International Standard for hCG (WHO) stimulated lymphoma cell replication after 72 h of exposure to the cells. The stimulation was dose dependent, beginning at 100 pg/ml and peaking at 10 ng/ml (140% vs. controls, P less than 0.001). Specific hCG antiserum (SB6) did not alter cell replication, but when added simultaneously with hCG, completely blocked the stimulation induced by hCG (10 ng/ml). No effect on cell proliferation was seen when the beta-subunit of hCG, the common glycoprotein alpha-subunit, human LH, FSH, or placental lactogen was added to the cells. These results indicate that hCG can stimulate proliferation of rat lymphoma cells in vitro. If hCG affects human tumors in a similar fashion, the ectopic production of the hormone by tumors may stimulate growth of the neoplasm.

Purified first and third trimester placental trophoblasts differ in in vitro hormone secretion.

In vitro studies with cytotrophoblasts obtained from term placentas have shown low levels of placental protein hormone secretion during the first 2 days in culture, followed by a marked increase during days 3 and 4. Since maternal serum placental hormone levels at term and during the first trimester differ, it is conceivable that cytotrophoblasts from first trimester placentas will differ in endocrine function from those derived from term placentas. Therefore, we examined the secretion of hCG, hCG alpha, human placental lactogen (hPL), and progesterone (P) both in the basal state and after exposure to 8-bromo-cAMP or endogenous cAMP stimulation with cholera toxin in cytotrophoblasts purified by enzymatic dispersion and Percoll gradient centrifugation from four first trimester and four third trimester placentas. At the time of seeding, all cells were mononuclear, and the degrees of aggregation and syncytia formation were similar in first and third trimester trophoblasts during the 4 days in culture. First trimester trophoblasts secreted greater quantities of hCG than did term trophoblasts, while basal secretion of hCG alpha, hPL, and progesterone were similar. Qualitative differences in the hormone secretory patterns were apparent. hCG secretion by first trimester trophoblasts decreased over the 4 days in culture, while the amounts secreted by third trimester trophoblasts increased. hCG alpha levels increased for 2-3 days in first trimester trophoblasts and then decreased, while hCG alpha increased in term trophoblast medium over the 4 days. The ratio of hCG alpha to hCG in media from first and third trimester cultures reflected the relative ratios of these hormones in placental tissue and maternal serum at analogous stages of pregnancy. hPL concentrations in the medium declined between days 3-4 in first trimester cultures, while they increased between days 3-4 in third trimester cultures. The secretory pattern of P was somewhat more erratic. cAMP stimulation led to a similar rise in hCG, hCG alpha, and P secretion in first and third trimester trophoblasts, and a variable response for hPL secretion. These results indicate that the functional activity of placental trophoblasts in culture depends in part upon the age of the placenta from which the cells are derived. The differences may represent intrinsic differences in function or the presence of inhibitory or stimulatory factors of maternal, fetal, or trophoblast origin.

Progesterone and human chorionic gonadotropin do not stimulate placental proteins 12 and 14 or prolactin production by human decidual tissue in vitro.

To investigate the regulation of the synthesis and secretion of placental proteins-12 (PP12) and -14 (PP14) and PRL, explants and enriched preparations of stromal cells and gland cells obtained from 10 human early pregnancy decidua were preincubated in medium for 24 h (baseline), followed by incubation in medium with or without progesterone (0.02-32 mumol/L), hCG (10 and 100 ng/ml), or cAMP (0.25-1 mmol/L) in an atmosphere of 5% CO2-95% air at 37 C for another 96-120 h. Media were changed each 24 h, and PP12, PP14, and PRL levels were determined by RIA. Decidual explants, as well as their isolated cells produced detectable levels of PP12, PP14, and PRL in vitro. The gland cells synthesized and secreted about 30 times more PP14 than did stromal cells. After 96-120 h of incubation, the production of each protein by control cultures was increased 81-167% compared to the baseline (not significant). The secretion of these proteins in medium supplemented with progesterone or hCG was not significantly different from that in the control groups. 8-Bromo-cAMP significantly increased the secretion of PRL and PP12, but not PP14, by stromal cells compared to control values. We conclude that 1) PP14 is mainly produced by decidual gland cells; 2) progesterone at the concentrations used in our study does not stimulate production of PP12, PP14, and PRL in decidualized endometrium in vitro; 3) hCG does not stimulate the production of PP12 and PP14 in decidualized endometrium; and 4) 8-bromo-cAMP stimulates decidual stromal cell secretion of PRL and PP12.

Discordant secretion of placental protein hormones in differentiating trophoblasts in vitro.

The regulation of trophoblast secretion of the placental proteins CG (hCG), placental lactogen (hPL), and pregnancy specific-beta-1-glycoprotein (SP-1) has not been fully elucidated. We therefore studied the secretion of hCG, hCG-beta subunit, hCG-alpha subunit, hPL, and SP-1, both in the basal state and after exposure to 8-bromo-cAMP, during the in vitro differentiation of cytotrophoblasts to syncytiotrophoblasts. Term placental tissue was enzymatically digested and cytotrophoblasts purified by Percoll density gradient centrifugation. At the time of seeding of 4-6 X 10(5) cells/ml in 35-mm flasks all of the cells were mononuclear and 48% contained hCG-alpha, but none contained hCG or hCG-beta by the avidin-biotin-peroxidase immuno-histochemical method. After 3 days in culture, hCG-alpha and hCG or hCG-beta were present in multinucleated syncytiotrophoblasts and in the mononuclear cytotrophoblasts. During the 5 days in culture, the secretion of hCG, hCG-alpha, hPL and SP-1 into the media increased and reached a maximum on day 4 followed by a decrease on day 5. Basal hCG-beta secretion was very low and did not change during culture. The ratio of hCG-alpha/hCG decreased from days 1-4 of culture. Incubation with 8-bromo-cAMP for 24 h stimulated the secretion of hCG and hCG-alpha, whereas hCG-beta and hPL levels did not change. The secretion of SP-1, however, was inhibited by 8-bromo-cAMP. These results indicate that the cytotrophoblasts secrete hCG, hCG-beta and hCG-alpha during in vitro differentiation into syncytiotrophoblasts. Since the basal ratio of hCG to hCG-alpha secretion changed during 5 days in culture and a cAMP analogue differentially modulated the secretion of the different placental protein hormones, the physiological regulation of secretion of each of the proteins also may differ.

Radiation-associated hyperparathyroidism: comparison of adenoma growth rates, inferred from weight and duration of latency, with prevalence of mitosis.

In sporadic parathyroid adenomas, the birth rate of new cells, based on the proportion of S-phase cells at the time of surgical excision, is much too low to account for growth of the tumor from a single cell, as is required by monoclonal origin, even if the mutation occurred in utero, indicating that the rate of cell proliferation has slowed down during the course of the disease. In radiation-associated hyperparathyroidism, the age at irradiation provides a more accurate upper limit to the age of the tumor. The purpose of this study was to relate this age to the prevalence of mitosis as an alternative index of current cell proliferation. In 56 such patients, the geometric mean for the minimum cell birth rate needed for growth from a single cell to the observed size in the time available was 54.4%. In 44 patients, including 31 of the previous 56 and an additional 13, sampling an average of 220,000 cell profiles, 15 mitoses were found, an overall prevalence of 0.15/10(5), which corresponds to a cell birth rate of 2.7%/yr, assuming the duration of mitosis to be 0.5 h. If cases with no mitosis were assigned a value of half the detection limit, the geometric mean mitotic index was 0.360/10(5), and the corresponding cell birth rate was 6.4%/yr. This is more than 8 times smaller than the minimum birth rate required and 20 times smaller than the cell birth rate in meningiomas, suggesting that such extreme reduction of cell birth rate is a unique feature of parathyroid adenomas, rather than a general feature of all benign tumors. The data support the set-point hypothesis, which reconciles the earlier concept of focal hyperplasia with monoclonal origin and provides an alternative nonneoplastic mechanism of etiology for the usual nonprogressive form of the disease.

The deactivation of hCG by nicking and dissociation.

Human chorionic gonadotropin (hCG) is composed of an alpha- and a beta-subunit, joined noncovalently. A proportion of hCG molecules in pregnancy serum and urine samples have nicks or a missing peptide linkage between either beta-subunit residues 44 and 45 or beta-subunit residues 47 and 48. These nicks ablate the steroidogenic activity of hCG. We examined the source of nicking, and the occurrence and stability of nicked hCG molecules produced during pregnancy. We investigated the source of nicking. Standard hCG was added to three samples of whole blood, and incubated 18 h at 37 C. No change in extent of nicking was detected. However, nicking of hCG beta-subunit was detected by gel electrophoresis (bands at M(r) = 17,000 and M(r) = 22,000, corresponding to the peptides beta 1-47(44) and beta 48(45)-145, respectively) in culture fluids from first trimester placental explants and from JAr malignant trophoblast cells. We inferred that nicking occurs before or immediately upon secretion by trophoblast tissue. We examined the occurrence of nicking. Levels of total hCG (nicked+nonnicked) and intact hCG (nonnicked) were determined in 233 serum and 168 urine samples from 4-40 weeks of pregnancy. From the two measurements the extent of nicking was estimated. A linear relationship was indicated between advancing weeks of gestation and increasing extent of nicking (regression analysis, months vs. percent nicked, 95% correlation). Minimum nicking was observed in serum from the first 2 months of pregnancy (mean = 9% of hCG molecules), increased nicking in the months after, and maximum nicking in samples from the last 2 months of pregnancy (mean = 21% of hCG molecules, t test first 2 months vs. last 2 months, P < 0.00005). Similar results were observed with urine samples (first 2 months mean = 9%, last 2 months = 27%, t test P < 0.00005). We concluded that nicking is more prevalent after the hCG peak (after 2 months of pregnancy). Finally, we examined the stabilities of nicked and intact hCG molecules. Standard hCG (batch CR127, 20% nicked) and hCG preparation C5 (100% nicked) were incubated for varying times in whole blood. C5 hCG dissociated rapidly into free alpha- and beta-subunits (dissociation half-life 22 +/- 5.2 h), over 30 times faster than standard hCG (dissociation half-life 700 h).(ABSTRACT TRUNCATED AT 400 WORDS)