Influence of common clinical variables on intraoperative parathyroid hormone monitoring during surgery for primary hyperparathyroidism.

BACKGROUND: Intraoperative monitoring of parathyroid hormone (IOPTH) is a reliable method of predicting the cure of primary hyperparathyroidism (PHPT). The aim of this study is to assess whether common clinical variables (CCV) frequently encountered in patients with PHPT may affect the magnitude of PTH drop or the likelihood of patients meeting the intraoperative cure criterion. DESIGN: Patients who were surgically cured from PHPT caused by single gland disease (SGD) and had full IOPTH protocol (4 measurements) were stratified according to age, gland weight, renal function, vitamin D status and severity of hypercalcemia. The percentage of IOPTH drop and the frequency of patients who had true positive IOPTH test results were compared among groups. RESULTS: 762 patients had surgery for PHPT, of whom 746 were (98%) cured. Of these 746 patients, 511 who had SGD and a full IOPTH protocol were included in this study. The median IOPTH drop was significantly higher among younger patients, those with severe hypercalcaemia at 5, 10, 15 min after gland excision, giant glands (at 5-min only), patients with vitamin D deficiency (at 10, 15 min), and those with normal renal function (at 15 min only). The likelihood of the patients meeting the intraoperative cure criterion was not significantly affected among the groups except in patients with mild hypercalcaemia, who were significantly less likely to have 50% IOPTH drop than those with severe hypercalcaemia at all time points. The frequency of mildly hypercalcaemic patients who met cure criterion was significantly improved by extending measurement to 15 min. CONCLUSIONS: IOPTH monitoring has the ability to mitigate the variability of IOPTH kinetics associated with most clinical variables. Mildly hypercalcemic patients in particular may benefit from waiting for 15-min measurement before any surgical decision is made.

Plasma aldosterone response to the low-dose adrenocorticotrophin (ACTH 1-24) stimulation test.

BACKGROUND: Endocrine tests for adrenal insufficiency use pharmacological doses of stimulant such as ACTH. More physiological tests have often used high-dose protocols for sampling frequency. AIMS: To evaluate the response of plasma aldosterone concentration to low doses (125, 250 and 500 ng/m(2) body surface area) of synthetic ACTH. DESIGN: A randomised trial in six normal adult males aged 18-27 years. MATERIALS AND METHODS: Aldosterone concentration was measured by radioimmunoassay in serum from blood samples taken at 10 min intervals for 90 min. RESULTS: All three doses produced a significant rise in plasma aldosterone concentration (125 ng/m(2), P = 0.003; 250 ng/m(2), P < 0.001; 500 ng/m(2), P < 0.001) but there was no effect of dose on either the peak or incremental plasma aldosterone concentration. Mean time to peak was similar between the doses and the two higher doses were associated with a longer secretory profile (125 ng/m(2) 56 (26 SD) mins, 250 ng/m(2) 74 (19) mins, 500 ng/m(2) 77 (21) mins; F = 3.39; P = 0.04). Peaks of 100% were detected within 30 min of drug administration and peak response was associated with the prestimulation plasma aldosterone concentration (r = 0.45; P = 0.003). The between- and within-individual coefficients of variation for prestimulation concentrations were 37.0% and 32.8%, and for the peak response were 27.2% and 27.2%, respectively. CONCLUSIONS: The response of plasma aldosterone concentrations to low-dose ACTH administration requires a blood sampling protocol of 0, 10, 20 and 30 min to capture concentrations near the peak response. The high-dose protocol would have missed the response. Over the dose range studied no dose-response was observed so the selection of dose should be based on the dose effective to release steroids in the glucocorticoid pathway if this study is to be used in conjunction with such evaluation.

Identification of neuroactive steroids and their precursors and metabolites in adult male rat brain.

Steroids in the brain arise both from local synthesis and from peripheral sources and have a variety of effects on neuronal function. However, there is little direct chemical evidence for the range of steroids present in brain or of the pathways for their synthesis and inactivation. This information is a prerequisite for understanding the regulation and function of brain steroids. After extraction from adult male rat brain, we have fractionated free steroids and their sulfate esters and then converted them to heptafluorobutyrate or methyloxime-trimethylsilyl ether derivatives for unequivocal identification and assay by gas chromatography analysis and selected ion monitoring mass spectrometry. In the free steroid fraction, corticosterone, 3alpha,5alpha-tetrahydrodeoxycorticosterone, testosterone, and dehydroepiandrosterone were found in the absence of detectable precursors usually found in endocrine glands, indicating peripheral sources and/or alternative synthetic pathways in brain. Conversely, the potent neuroactive steroid 3alpha,5alpha-tetrahydroprogesterone (allopregnanolone) was found in the presence of its precursors pregnenolone, progesterone, and 5alpha-dihydroprogesterone. Furthermore, the presence of 3beta-, 11beta-, 17alpha-, and 20alpha-hydroxylated metabolites of 3alpha,5alpha-tetrahydroprogesterone implicated possible inactivation pathways for this steroid. The 20alpha-reduced metabolites could also be found for pregnenolone, progesterone, and 5alpha-dihydroprogesterone, introducing a possible regulatory diversion from the production of 3alpha,5alpha-tetrahydroprogesterone. In the steroid sulfate fraction, dehydroepiandrostrone sulfate was identified but not pregnenolone sulfate. Although pharmacologically active, identification of the latter appears to be an earlier methodological artifact, and the compound is thus of doubtful physiological significance in the adult brain. Our results provide a basis for elucidating the origins and regulation of brain steroids.

Primary glucocorticoid receptor defect with likely familial involvement.

A 29-year-old woman with moderately elevated blood pressure and signs of hyperandrogenism (hirsutism and acne) but without typical Cushing's syndrome symptoms has been followed for almost 6 years. Steroid and glucocorticoid receptor studies indicated a primary glucocorticoid receptor defect. Elevated androgen values were of special interest. Clinical manifestation of hyperandrogenism seemed not to be proportional to the biochemical findings. Therefore, the possibility of a partial androgen receptor defect should also be considered.

Potential pitfalls in intraoperative parathyroid hormone measurements during parathyroid surgery.

BACKGROUND: The outcome of parathyroid surgery is often not clear for at least 24 h after the operation. A frozen section does not always distinguish between an adenoma and hyperplasia. Minimally invasive surgical techniques are being refined, so the need for perioperative assurance about the completeness of surgery has increased. The value of intraoperative parathyroid hormone (PTH) measurements in 26 surgical cases undergoing parathyroidectomy has been evaluated. METHODS: Twenty-one patients were diagnosed as having primary hyperparathyroidism, including two patients with multiple endocrine neoplasia type I (MEN I). Five patients had tertiary hyperparathyroidism, including one patient with X-linked hypophosphataemia and four with renal hyperparathyroidism (RHPT). Blood samples were taken at the onset of surgery, at the time of tumour resection and at 5-min intervals following removal of the tumour. PTH was measured using a PTH Turbo assay on the DPC Immulite analyser. RESULTS: Current practice suggests that the PTH concentration should fall to less than 50% of the pre-incision value or to less than 50% of the level at the time of tumour resection (time equals zero). PTH levels were therefore monitored at 5-min intervals following removal of the tumour. In most of the case studies PTH followed the suggested pattern, but not when further exploration was warranted to determine if another adenoma was present. In some cases the PTH levels fell by the appropriate margin to deem the procedure a success but at 10 min post-gland excision the PTH began to rise again. Further exploration was required to confirm the continued source of PTH. CONCLUSION: We recommend that intraoperative PTH measurements continue until at least 15 min post-gland removal in cases of suspected single-gland disease. A decline in PTH concentration to at least 50% of the pre-incision or time of gland resection levels should be observed. If the PTH remains elevated or rises again after an appropriate decrease in levels, then multigland disease or ectopic sources should be considered. Caution is recommended in interpreting intraoperative PTH measurements to ensure complete success of the surgical procedure.

Single strand conformation polymorphism (SSCP) analysis for the detection of mutations in the CYP11B1 gene.

The adrenal 11 beta-hydroxylase is a mitochondrial P450 enzyme encoded by the CYP11B1 gene, which is situated on chromosome 8q22 in tandem with the gene for aldosterone synthase (CYP11B2). Deficiency of 11 beta-hydroxylase results in the inability to convert 11-deoxycortisol to cortisol and accounts for 5-8% of cases of congenital adrenal hyperplasia. In the following study the CYP11B1 genes from eight individuals with 11 beta-hydroxylase deficiency were screened for mutations using single strand conformation polymorphism (SSCP) analysis. Sequence analysis of variant exons revealed a 28 bp deletion and a 5 bp duplication exon 2 and five missense mutations, G267R, G267D, Q356X, R427H and C494F, distributed throughout the gene. One of these mutations, G267R, and a G to A transversion at the third nucleotide position of codon 318 occur at the +1 position of the splice donor sites. Mutations were neither the result of gene conversion nor nonhomologous recombination between the two closely related CYP11B genes.

Metabolism of radiolabeled corticosterone in an adult with the 17 alpha-hydroxylase deficiency syndrome.

[4-14C]Corticosterone was administered to a woman with the 17 alpha-hydroxylase deficiency syndrome and urine was collected for 72 h. Sixty-three percent of the radioactivity was eliminated on the first day, 10.3% on the second, and 3.8% on the third, making a total recovery of 77%. On the first day, 85% of the recovered radioactivity was in the glucuronide conjugates of corticosterone, 10.6% was in the sulfate form of this steroid, and 3.9% was in the free forms of the steroid. On the following 2 days, the proportion of labeled glucuronides and free steroids decreased and that of labeled sulfates increased. On the first day of collection, the major radiolabeled metabolites were 21-hydroxylated steroids (e.g. allo-tetrahydrocorticosterone and 5 alpha- and beta-pregnane-3 alpha,11 beta,20 alpha,21-tetrol), but by the third day, at least 75% of the excreted activity was associated with 21-deoxysteroids, such as 3 alpha,20 alpha-dihydroxy-5 alpha (and beta)-pregnan-11-one and 5 alpha- and beta-pregnane-3 alpha,11 beta,20 alpha-triol. Bacterial metabolism in the intestinal tract is responsible for the dehydroxylation. 6 alpha-Hydroxytetrahydrocorticosterone was tentatively identified among several new metabolites of corticosterone.

Analysis of steroids in urine for differentiation of pseudohypoaldosteronism and aldosterone biosynthetic defect.

The salt-losing syndromes in the neonatal period and early infancy due to adrenal disease can be differentiated by the pattern of excretion of steroids in urine. The presence or absence of metabolites of cortisol, aldosterone, and corticosterone as well as certain precursors can be established in a single analysis of steroids in urine by using gas chromatography with open tubular capillary columns. The profiles of steroid excretion in the urine of 8 infants with renal tubular insensitivity to aldosterone were compared with those in 5 infants with isolated aldosterone biosynthetic defects. The excretion in urine of 18 hydroxytetrahydro-compound A was elevated in all 13 children, but relative to the excretion of tetrahydroaldosterone, a high ratio was found for the biosynthetic defect and clearly distinguished the 2 conditions. Age-related changes in steroid metabolism are described. The diagnosis in each case was supported by clinical investigation together with determinations of PRA and aldosterone concentrations.

Deficient 3 beta-hydroxy-5-ene steroid secretion by newborn infants.

Congenital adrenal hypoplasia is reported in two siblings. The first died at 16 months of purulent bronchopneumonia after a history of adrenal insufficiency. No gross adrenal tissue was found at autopsy and urinary steroids were not excreted in detectable amounts before death. In a subsequent uncomplicated pregnancy, extremely low estrogens were recorded in the last trimester. Analysis of steroids in the urine of the neontate by gas chromatography revealed virtual absence of 3 beta-hydroxy-5-ene steroids. These suggest hypoplasia of the fetal adrenal cortex. Metabolites of cortisol were excreted in normal amounts and responded adequately to ACTH stimulation. Neonatal hyponatremia was associated with subnormal excretion of corticosterone and aldosterone metabolites. It is proposed that in the perinatal period, the fetal zone is required for mineralocorticoid synthesis, possibly by providing essential precursor steroids, e.g. 21-hydroxypregnenolone.

Cortisol, androstenedione (A4), dehydroepiandrosterone sulphate (DHEAS) and 17 hydroxyprogesterone (17OHP) responses to low doses of (1-24)ACTH.

The dose of 250 microg used in the standard short synacthen test is supraphysiological and lower doses may provide a more sensitive test. We examined steroid responses to 125ng/m2, 250ng/m2 and 500 ng/m2 (1-24)ACTH in 6 normal males, looking at effects of dose and the within- and between-subject coefficients of variation (CV). Subjects were given each dose 3 times, blood samples were taken at 10 minute intervals. There was a dose response relationship between dose of (1-24)ACTH and peak values for cortisol and 17OHP (p<0.05). There was no difference between peaks of A4 at different doses and no clear peaks were reached for DHEAS. 86% of the peaks for 17OHP, 63% for A4 and 25% for cortisol were at 10 minutes and 14%, 29% and 65% respectively at 20 mins (p=0.001). Within-subject CV for cortisol was 12.6% and between subject 10.1%. Tests of adrenal function using low doses of (1-24)ACTH have acceptable between- and within-subject CV for peak values with a dose as low as 125 ng/m2 (1-24)ACTH. Protocols for low dose synacthen tests, with traditional sampling at zero, 30 and 60 minutes or even as shown here at 10 minute intervals, fail to fully define the changes in steroid levels following adrenal stimulation. More frequent blood sampling will be needed to accurately detect peak levels in particular of 17OHP and A4.

Hypertension in a four-year-old child: gas chromatographic and mass spectrometric evidence for deficient hepatic metabolism of steroids.

A 4-yr-old boy with hypertension and hypokalaemic alkalosis had low plasma aldosterone levels and renin activity. The hypertension and hypokalemia responded to spironolactone and triamterene therapy. A partial response to dexamethasone was observed. Analysis of urinary steroid metabolites by gas chromatography-mass spectrometry showed that the excretion of metabolites of deoxycorticosterone and aldosterone was subnormal, and there was no evidence for sizeable excretion of unusual steroids with potential mineralocorticoid activity. The cortisol excretion rate, however, was subnormal, and the relative excretions of individual metabolites of this hormone were not typical. In particular, the excretion of tetrahydrocortisone was markedly reduced, and the excretions of allotetrahydrocortisol and free cortisol and metabolites were elevated. These findings suggest that modified or deficient metabolism of adrenal steroids could give rise to elevated blood pressure. It is not known whether the inappropriate production of unusual cortisol metabolites were responsbile for the high blood pressure or whether the altered metabolism is indicative of similar abnormality in the metabolism of other adrenal steroids, resulting in hyperproduction or extended half-life of minor but highly active mineralocorticoids of unknown structures.

11 beta-Hydroxysteroid dehydrogenase and its inhibitors in hypertensive pregnancy.

Preeclampsia is accompanied by amplification of the sodium retention that is a feature of normal pregnancy. Recent evidence suggests that mineralocorticoid receptor activation is increased in preeclampsia, but classic mineralocorticoids (aldosterone, 11-deoxycorticosterone) are not present in excess. Cortisol can act as a mineralocorticoid receptor agonist only when its renal inactivation to cortisone by 11 beta-hydroxy-steroid dehydrogenase is impaired, for example, in congenital enzyme deficiency and after administration of exogenous inhibitors (eg, licorice). Endogenous inhibitors of this enzyme have been detected in human urine and are increased in pregnancy. To establish whether cortisol causes mineralocorticoid excess in hypertensive pregnancy and whether endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase are responsible, we studied 25 hypertensive pregnant patients (13 with preeclampsia and 12 with gestational hypertension), 16 normotensive pregnant subjects, and 13 nonpregnant control subjects. Concentrations of plasma renin and aldosterone were increased in pregnancy, but less so in hypertensive pregnancy. Plasma potassium and urinary electrolytes were not different between the groups. Plasma cortisol was increased in pregnancy but not different in hypertensive pregnancy, and urinary cortisol, plasma and urinary cortisone, and urinary tetrahydrocortisol and tetrahydrocortisone were not different between the groups. Endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase were more active in urine from pregnant women but were not increased further in hypertensive pregnancy. There were no differences in these parameters between patients with preeclampsia and gestational hypertension. We conclude that deficient inactivation of cortisol to cortisone does not contribute to the sodium retention of normotensive or hypertensive pregnancy and that endogenous inhibitors of 11 beta-hydroxysteroid dehydrogenase have no evident pathophysiological significance in pregnancy.

Intermediates in 16-androstene biosynthesis in neonatal porcine testis.

The metabolism of pregnenolone has been studied in microsomal preparations of testes from 3-week old piglets. Metabolites identified after derivatization by capillary gas-chromatography and further by combined gas chromatography-mass spectrometry were: 17-hydroxy- and 16 alpha-hydroxypregnenolone, dehydroepiandrosterone, 5-androstenediols, 5-pregnenediol and andien-beta. Pregnenolone and 16-dehydro-pregnenolone, previously not separable by other methods, were successfully resolved as methyl oximetrimethylsilyl ethers using capillary column gas-chromatography.

Antibiotics attenuate experimental hypertension in rats.

Hypertension was produced in Sprague-Dawley rats by intramuscular injections of either corticosterone or ACTH. Lower increases in blood pressure to these challenges were observed in Sprague-Dawley rats pretreated with neomycin or vancomycin which alone had no effect on blood pressure or growth. The development of high blood pressure in spontaneously hypertensive rats of a stroke-prone substrain was also attenuated by oral administration of neomycin. These results suggest that experimental hypertension can be modulated by the administration of antibiotics.

Reproducibility of the cortisol response to stimulation with a low dose of ACTH(1-24): the effect of basal cortisol levels and comparison of low-dose with high-dose secretory dynamics.

We compared the reproducibility and repeatability of the acute adrenal response to low doses (90 and 500 ng/1.73 m2) of Synacthen (ACTH(1-24)) with that of the standard dose (250 micrograms/1.73 m2). We also examined the effect of basal cortisol levels on peak values achieved after stimulation with a low dose. ACTH(1-24) was given to six male volunteers: 90 ng/1.73 m2 twice at 90-min intervals on day 1, and 90 and 500 ng/1.73 m2 once on day 2 and 250 micrograms/1.73 m2 once on day 3. The rise in serum cortisol concentration with repeated low doses of ACTH was not attenuated (161 +/- 49 (S.D.) nmol/l on initial vs 150 +/- 41 nmol/l on repeat stimulation; P = 0.5) and this was reproducible (161 +/- 49 nmol/l on day 1 vs 148 +/- 15 nmol/l on day 2; P = 0.6). A dose of 500 ng ACTH(1-24)/1.73 m2 produced a maximal adrenal response in that the rise in serum cortisol concentration at 20 min was identical with that produced at the same time by the standard dose of 250 micrograms/1.73 m2. There was a strong positive correlation between the basal cortisol level and peak cortisol concentration after low-dose ACTH stimulation (r = 0.93, P < 0.001) but not between the basal cortisol level and the incremental rise (r = -0.1, P = 0.69). These results suggest that the cortisol response to low-dose ACTH stimulation is reproducible and not attenuated by repeat stimulation at 90-min intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of low doses of ACTH in the investigation of adrenal function in man.

We have investigated the adrenal response, in eight healthy adult men, to low doses of ACTH(1-24) in order to define a dose which will elicit a response similar to that obtained with the short Synacthen test. The studies were performed at 14.00 h and blood samples were withdrawn at 5-min intervals after an i.v. bolus injection of ACTH(1-24). The sampling interval was crucial in determining the timing of the peak response. Using sampling times of 0, 10, 15, 20, 25 and 30 min ensured detection of 47 out of 48 peaks. A dose-dependent rise in plasma cortisol concentration was observed with bolus injections of ACTH(1-24) between 30 and 250 ng/1.73 m2 body surface area. Increasing the dose to 500 ng/1.73m2 (500 times less than that used in the short Synacthen test) elicited an increment of plasma cortisol concentration of 200 nmol/l or greater in all subjects. Pretreatment with dexamethasone (1 mg) did not alter the timing of the peak cortisol concentration but blunted the increase (pretreatment: median, 159 nmol/l; range 83-239; on dexamethasone; median 62 nmol/l; range 21-207; P = 0.04). These data suggest that a dose of ACTH(1-24) of 500 ng/1.73 m2 satisfies the criteria of the short Synacthen test and may provide a useful method of investigating adrenal function.

Problems in diagnosis and management of congenital adrenal hyperplasia due to 21-hydroxylase deficiency.

A number of biochemical tests have been utilized to assist the diagnosis of steroid 21-hydroxylase deficiency. The specificity and accuracy of plasma 17-hydroxyprogesterone assays are important. A profile of steroids in urine by gas chromatography and mass spectrometry is the definitive test. Molecular biology is not practical for the diagnosis of a new case. The ACTH stimulation test for detection of heterozygotes is a poor discriminant. Fertility in patients with congenital adrenal hyperplasia may be due to excess of progesterone as well as of androgens. Gene amplification offers the best approach in molecular biology for the prenatal diagnosis of 21-hydroxylase deficiency.

Genetic analysis of the steroid 21-hydroxylase gene following in vitro amplification of genomic DNA.

The 5' end of the steroid 21-hydroxylase B gene encompassing putative control regions and the first 3 exons, has been selectively amplified in vitro from a number of patients with congenital adrenal hyperplasia caused by a deficiency of this enzyme. Sequence analysis has revealed a number of isolated instances of gene conversion to the 21-hydroxylase A sequence. One mutation, a C to G transversion at the 3' end of the second intron, thought to lead to incorrect splicing of the mRNA, was found in 11 subjects all with the classical form of the disease.

Studies to confirm the source of 11 beta-hydroxyandrostenedione.

In a longitudinal study of 82 children we found a gradual rise in median plasma concentrations of 11 beta-hydroxyandrostenedione (11 beta-OH-A4) from 2.5 to 6.4 nmol/l during childhood which was similar in both sexes. This could reflect changes in adrenal function during the adrenarche and sexual maturation. Plasma concentrations of 11 beta-OH-A4 in adults follow the patterns of cortisol secretion. In patients with diseases of the adrenal cortex, the plasma concentrations of 11 beta-OH-A4 were consistent with the pathology of each condition. In women with polycystic ovaries (PCO) undergoing gonadotrophic stimulation for in vitro fertilization and embryo transfer, 11 beta-OH-A4 (median = 3.8 nmol/l), testosterone and androstenedione, were raised when compared to women with normal ovaries (11 beta-OH-A4 median = 2.6 nmol/l). Follicular fluid has concentrations of 11 beta-OH-A4 six to twelve times greater than plasma levels and in women with PCO, 11 beta-OH-A4 concentrations were lower than in women with normal ovaries, which is consistent with an inhibition of ovarian 11 beta-hydroxylase. Granulosa cells in vitro demonstrated the production of 11 beta-OH-A4 by side chain cleavage of cortisol. These data support an adrenal source for 11 beta-OH-A4 but the raised plasma concentrations in women with polycystic ovary syndrome (PCOS) may reflect the excess androgen output from the ovary. 11 beta-OH-A4 may therefore be an additional marker for ovarian dysfunction.

The determination of 11 beta-hydroxyandrostenedione in human follicular fluid and plasma.

The development of a chromatographic/immunoassay method is presented for the measurement of 11 beta-hydroxyandrostenedione (11 beta-OH-A4) in ovarian follicular fluid (FFL) and plasma from women undergoing embryo transfer for in vitro fertilization. This method incorporates high-performance liquid chromatography (HPLC) and permits the simultaneous measurement of other steroids from a single sample in order to assess the intraovarian environment. Authenticity of 11 beta-OH-A4 in follicular fluid was confirmed using selected ion monitoring (SIM) gas chromatography/mass spectrometry (GC/MS). Our results demonstrate a mean concentration of 18.6 nmol/l in follicular fluid compared with 3.2 nmol/l in plasma. The origin of 11 beta-OH-A4 in follicular fluid requires further investigation but these findings supports the hypothesis of ovarian 11 beta-hydroxylase activity on C19 steroids.