The combination of soluble tumor necrosis factor receptor type 1 and fibroblast growth factor 21 exhibits better prediction of renal outcomes in patients with type 2 diabetes mellitus.

PURPOSE: Numerous biomarkers of diabetic kidney disease (DKD) are associated with renal prognosis but head-to-head comparisons are lacking. This study aimed to examine the association of soluble tumor necrosis factor receptor type 1 (sTNFR1), fibroblast growth factor 21 (FGF-21), endocan, N-terminal pro-brain natriuretic peptide (NT-pro-BNP), and renal outcomes of patients with or without clinical signs of DKD. METHODS: A total of 312 patients were enrolled in a prospective observational study that excluded individuals with estimated glomerular filtration rates (eGFR) < 30 mL/min/1.73 m2. Composite renal outcomes included either a > 30% decline in eGFR and worsening albuminuria or both from consecutive tests of blood/urine during a 3.5-year follow-up period. RESULTS: Higher sTNFR1 and FGF-21, rather than endocan and NT-pro-BNP, levels were associated with renal outcomes but the significance was lost after adjusting for confounders. However, sTNFR1 levels ≥ 9.79 pg/dL or FGF-21 levels ≥ 1.40 pg/dL were associated with renal outcomes after adjusting for the confounders (hazard ration [HR] 2.76, 95% confidence interval [CI] 1.36-5.60, p = 0.005 for sTNFR1 level; HR 1.95, 95% CI 1.03-3.69, p = 0.03 for FGF-21 level). The combination of both levels exhibited even better association with renal outcomes than did either one alone (adjusted HR 4.45, 95% CI 1.86-10.65, p = 0.001). The results were consistent among patients with preserved renal function and normoalbuminuria. CONCLUSION: Both sTNFR1 and FGF-21 levels were associated with renal outcomes of in patients with type 2 diabetes, and the combination of the abovementioned markers exhibits better predictability.

Diagnosis of insulin resistance in hypertensive patients by the metabolic syndrome: AHA vs. IDF definitions.

BACKGROUND: Subjects with the metabolic syndrome are accompanied by insulin resistance (IR). However, it is not clear how well the newly defined metabolic syndrome identifies IR specifically in hypertensive subjects. AIMS: The purpose of the study was to evaluate the performance of the metabolic syndrome, defined by the American Heart Association (AHA) and the International Diabetes Federation (IDF) definitions, in identifying IR in hypertension. METHODS: The analysis is a cross-sectional study. Totally, 228 hypertensive patients and 92 non-diabetic normotensive controls who received insulin suppressive tests for direct evaluation of their insulin sensitivity were included from the Stanford Asia and Pacific Program for Hypertension and IR. McNemar's tests were used to compare sensitivity and specificity of the AHA-defined with the IDF-defined metabolic syndrome in diagnosis of IR. RESULTS: The sensitivity of the metabolic syndrome for IR in hypertension was 89.7% and the specificity 45.9% by the AHA definition. Using the IDF definition, the sensitivity was 77.6%, and the specificity increased to 63.5%. The diagnostic power of individual components of the syndrome was also modest. The predictive discrimination of wider waist circumference was similar to that of the AHA-defined metabolic syndrome. CONCLUSIONS: Use of the metabolic syndrome by the AHA definition provided good sensitivity, but low specificity to diagnose IR in hypertension. The IDF definition improved in false-positive rate, but it was still not specific enough to identify IR in hypertension.

Surrogate estimates of insulin sensitivity in subjects with hypertension.

The purpose of the study is to compare surrogate estimates of insulin sensitivity with a directly measured insulin sensitivity index, steady-state plasma glucose (SSPG) from insulin suppression test (IST), in subjects with hypertension. Two hundred and twenty-eight hypertensive patients who received IST for SSPG were included for analysis. Estimates from fasting measurements alone, homeostasis model assessment for insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI)), and indices from fasting and/or 2 h samples (ISI(0,120) and ISI(TX)) were calculated. In addition to Pearson and partial correlations, variance-component models were used to test the relationship between surrogate estimates of insulin sensitivity and SSPG. A large proportion of variance owing to covariates in the variance-component models indicated the goodness of model fit, irrespective of the independence among variables. SSPG was positively correlated with logarithmic transformation (Log) (HOMA-IR) and negatively correlated with QUICKI, Log (ISI(0,120)) and ISI(TX) (all P<0.0001). Log (ISI(0,120)) seemed to have a better correlation with SSPG (r=-0.72) than other measures in partial correlation. The proportion of variance owing to all covariates of Log (ISI(0,120)) and ISI(TX) were larger than those of Log (HOMA-IR) and QUICKI in the variance-component models. After adjustments for demographic and obesity covariates, the proportion of variance explained by Log (ISI(0,120)) were largest among the surrogate measures in the variance-component models. Our results showed that ISI(0,120) and ISI(TX) correlated better with SSPG than those used fasting measures alone (HOMA-IR and QUICKI). Log (ISI(0,120)) currently showing the strongest association with SSPG than other estimates is adaptable for use in large studies of hypertension.

Growth hormone (GH) replacement reduces total body fat and normalizes insulin sensitivity in GH-deficient adults: a report of one-year clinical experience.

The effects of GH replacement on body fat composition and insulin sensitivity were assessed in GH-deficient adults. The patients were randomized into a double-blind, placebo-controlled study of human recombinant GH replacement therapy for 6 months (period 1), followed by an open phase of GH for another 6 months (period 2). Anthropometric variables, body fat composition (fat %), and biochemical parameters were measured during the trial. Measurements of in vivo insulin sensitivity were carried out at the commencement of the study and on completion of the trial by modified insulin suppression test. The modified insulin suppression test was performed both in the morning (AM) and in the afternoon (PM) to further evaluate the PM-AM steady-state plasma glucose (SSPG) pattern. We found that the GH-deficient adults had more body fat and were insulin resistant. Significant reduction in fat % and total body fat mass was found in the active arm of period 1 without alteration of body weight. Besides, we demonstrated, for the first time, the GH replacement for 6 months did not alter the insulin sensitivity, but replacement for a longer period (12 months) normalized not only the AM SSPG level but also the PM-AM SSPG pattern. We also found a positive correlation between SSPG (regardless of AM vs. PM) and fat % and total body fat mass. In conclusion, normalization of insulin sensitivity in GH-deficient adults after replacement of GH may be related to the reduction of total body fat.

Alterations with age of the T3-stimulated release of atrial natriuretic peptide and its effect on water and sodium metabolism in rats.

The influence of age on urinary excretion of sodium and water and in vitro release of atrial natriuretic peptide (ANP) were studied in rats. Older rats had increased daily water intake and urine output. They also had increased plasma ANP, decreased right atrial contents of ANP and increased ANP release in response to 10 nM T3. The ageing process may have altered the regulatory mechanisms of water metabolism and secretion of ANP.

Linoleic acid and oleic acid increase the endothelin-1 binding and action in cultured rat aortic smooth muscle cells.

An increase in circulating non-esterified fatty acids (NEFA) has been observed in patients with poorly controlled diabetes mellitus. To investigate whether fatty acids will affect the endothelin-1 (ET-1) receptor and thus contribute to the acceleration of atherosclerosis in diabetic patients, cultured rat aortic smooth muscle cells (SMC) were maintained in media containing higher (similar to those in diabetic patients) concentrations of oleic acid (OA) or linoleic acid (LA). The ET-1 binding and ET-1-stimulated thymidine uptake were then examined. We found that cells treated with OA (500 micromol/L) or LA (250 micromol/L) showed a significant increase in ET-1 receptor amount as demonstrated by Scatchard analysis (Bmax: 7.40 +/- 1.04 v 2.71 +/- 0.54 fmol/mg and 5.00 +/- 1.00 v 3.32 +/- 0.70 fmol/mg, respectively). No change in binding affinity was found. Moreover, both the basal and ET-1-stimulated thymidine uptake were enhanced by treatment with either LA (basal, 11,367 +/- 4,117 cpm/mg; LA, 13,933 +/- 4,003 cpm/mg; ET-1 (10(-8)), 16,931 +/- 4,412 cpm/mg; LA +/- ET-1 (10(-8)), 28,855 +/- 5,217 cpm/mg) or OA (basal, 4,912 +/- 1,193 cpm/mg, OA, 8,027 +/- 1,318 cpm/mg; ET-1 (10(-8)) 9,947 +/- 2,520 cpm/mg; OA + ET-1 (10(-8)), 16,761 +/- 1,740 cpm/mg). This enhancement in thymidine uptake was associated with an increase in cell number. Because ET-1 and its receptor are involved in atherogenesis, our findings suggested that increase in circulating NEFA may contribute to the acceleration of atherosclerosis in diabetic patients. Further studies to confirm its role in the vascular wall are warranted.

Effects of methanol extract of Chansu on hypothalamic-pituitary-testis function in rats.

Chansu, a galenical preparation of the dried white venom of Chinese Bufo bufo gargarizans, is one of the major components of Kyushin, a traditional Chinese medicine. Kyushin is reported to have a cardiotonic effect that has been suggested to be due to the action of bufadienolides such as bufalin and cinobufagin. Recently, we found that administration of bufalin in male rats diminished the luteinizing hormone (LH) response to gonadotropin-releasing hormone (GnRH) and the secretion of testosterone both in vivo and in vitro. These observations suggest that Chansu may possess hypogonadal effects in male rats. In the present study, the effects of the methanol extract of Chansu on hypothalamic-pituitary-testicular function in male rats were examined. Crude Chansu was extracted by methanol and purified by a Sep-Pak C18 column. No activity of bufalin, cinobufagin, estradiol, or digoxin in purified methanol extract was detected; all Chansu used in this study was the purified methanol extract. A single intravenous injection of Chansu resulted in a decrease of the basal (20% to 55%) and human chorionic gonadotropin (hCG)-induced (35% to 40%) levels of plasma testosterone and the GnRH-induced level of plasma LH (25% to 30%). Administration of Chansu in vitro decreased basal and hCG-stimulated testosterone production by 60% to 70% and 40% to 60%, respectively, as well as spontaneous and forskolin- or 3-isobutyl-1-methylxanthine (IBMX)-induced accumulation of adenosine 3',5'-cyclic monophosphate (cAMP) by 30% to 45% in rat testicular interstitial cells. Although LH release by rat anterior pituitary glands was diminished, GnRH release by the rat mediobasal hypothalamus was enhanced by administration of Chansu in vitro. These results suggest that the bufalin-free extracts of Chansu inhibit testosterone secretion in rats, in part, due to (1) a decreased production of testicular cAMP, (2) a decreased response of testosterone to gonadotropin, and (3) a reduction of the LH response to GnRH.

Exacerbation of insulin resistance and postprandial triglyceride response in newly diagnosed hypertensive patients with hypertriglyceridaemia.

The purpose of the study is to examine the differences in insulin resistance and postprandial triglyceride (TG) response between hypertensive patients with or without hypertriglyceridaemia. The study is a comparative cohort study with matching. Thirty-one newly diagnosed hypertensive patients without any medication were recruited from a health survey. The participants were further divided into two groups: those with fasting TG <2.26 mmol/L, and those with TG between 2.26 and 5.65 mmol/L. Both groups were matched in age, sex, body mass index and waist circumference. Each patient received a 75-g oral glucose tolerance test, an insulin suppression test, and a 1000 kcal high fat mixed meal test. The hypertriglyceridaemic hypertensive patients had significantly higher fasting insulin, 2-h plasma glucose, 2-h insulin, and steady-state plasma glucose (SSPG) (13.16 +/- 1.87 vs 9.76 +/- 3.18 mmol/L). They also had a greater postprandial TG response to the challenge of mixed meal (DeltaAUC 20.76 +/- 10.06 vs 7.97 +/- 3.18 mmol 8 h/L). The postprandial TG response was closely correlated (r = 0.72-0.95, P < 0.0001) with fasting TG in all hypertensive patients. Both fasting TG levels and postprandial TG response were significantly (P < 0.05) correlated with SSPG. In conclusion, the hypertensive patients with hypertriglyceridaemia were more insulin resistant than those without it. Exacerbation of postprandial hypertriglyceridaemia was identified in these patients. The TG response to the challenge of high fat meal was significantly correlated with fasting TG and insulin resistant in them. The results provide a rationale for the alleviation of insulin resistance and hypertriglyceridaemia in these atherosclerosis-prone hypertensive patients.

Sagittal abdominal diameter is associated with insulin sensitivity in Chinese hypertensive patients and their siblings.

The purpose of the study is to observe the relation between anthropometric measurements, focusing on sagittal abdominal diameter (SAD), and insulin sensitivity indices in Chinese hypertensive patients and their siblings. In total, 907 participants, 537 hypertensive and 370 nonhypertensive, from 311 Taiwanese families were drawn from the Stanford Asia and Pacific Program for Hypertension and Insulin Resistance for the study. The participants received anthropometric measurements and 75-g oral glucose tolerance tests after an overnight fast. Fasting insulin, homeostasis model assessment for insulin resistance (HOMA-IR), and the insulin sensitivity index ISI(0,120) were chosen as surrogate measures of insulin sensitivity. In addition to Pearson and partial correlations, we used generalized estimating equations (GEEs) to examine the association between anthropometric measurements and insulin sensitivity indices. A small deviance in the GEEs indicates the goodness of model fit, irrespective of the independence among variables. The hypertensive patients were older in age, wider in waist circumference (WC), larger in body mass index (BMI) and SAD, and more insulin resistant than the nonhypertensive counterparts. The logarithmic transformation of fasting insulin, HOMA-IR, and ISI(0,120) significantly correlated with SAD, WC, and BMI before and after adjustments for age and sex. The deviances of SAD in the GEEs were similar to those of WC in all subjects, while BMI had smaller deviances than SAD and WC in the hypertensive patients. Our results suggest that the performance of SAD in predicting insulin sensitivity is comparable with WC in Chinese hypertensive patients and their siblings. BMI, however, seems to have better association with insulin sensitivity than SAD and WC in the patients with hypertension.

A comparison of insulin suppression tests performed with somatostatin and octreotide with particular reference to tolerability.

To evaluate the tolerability of insulin suppression test (IST) using octreotide instead of somatostatin, we compared the steady-state plasma glucose (SSPG) values and the safety during and after the test in 17 normal volunteers. The subject received IST twice (with somatostatin or with octreotide) in random order. During the test, all subjects were infused with regular insulin and glucose simultaneously for 180 min. In addition, either somatostatin or octreotide was infused intravenously over the same period of time. Plasma glucose, insulin and C-peptide were measured. The subject response to the test was recorded during and one day after the test by a structured questionnaire. The SSPG and the steady-state plasma insulin (SSPI) values reached during IST were similar, irrespective of the use of somatostatin or octreotide. There was a positive correlation between the SSPG values obtained from both methods (r = 0.67, P = 0.003). However, the mean intra-individual coefficient of variation is 17.9% for SSPG. The SSPG levels, no matter from which method, correlated positively with the 2-h insulin after oral glucose challenge. Most adverse events (especially gastrointestinal discomfort) occurred after the test, and increased much more after using octreotide than somatostatin (P = 0.002 by chi 2 test). In conclusion, the SSPG values measured by IST using octreotide or somatostatin are similar in normal healthy subjects. Yet, the octreotide method has more adverse events after the test.

Acipimox attenuates hypertriglyceridemia in dyslipidemic noninsulin dependent diabetes mellitus patients without perturbation of insulin sensitivity and glycemic control.

Hyperlipidemia, hypertriglyceridemia in particular, is a common feature in patients with noninsulin dependent diabetes mellitus (NIDDM) and may associate with insulin insensitivity. Acipimox, being widely prescribed for treating hypertriglyceridemia, is also used in NIDDM patients for their dyslipidemia. In the present study, we evaluated the effect of acipimox in Chinese NIDDM patients with hypertriglyceridemia. A total of 16 patients enrolled in a double-blind, randomized, placebo-controlled and two-period crossover study. After an 8 week run-in period, patients were randomly assigned into two groups receiving either acipimox (250 mg, twice daily) or placebo treatment. A total of 12 weeks later, these two groups switched their treatment for an additional 12 weeks. Blood samples were collected at the end of the run-in period and then at 4-week intervals in the whole study for lipid profile. A modified insulin suppression test was performed at the ends of the run-in period, 12-week and 24-week treatment to assess changes in insulin sensitivity. Our results showed that acipimox significantly lowered serum total triglyceride while compared to those by placebo. However, no difference was observed in serum non-esterified fatty acid, low-density lipoprotein cholesterol, total cholesterol (TC), high density lipoprotein-cholesterol (HDL-C) and HDL-C/ TC ratio between the two groups. Furthermore, glycemic indices and insulin sensitivity were similar during the base-line, placebo or acipimox periods. Taken together, our data suggest that acipimox significantly lowered TG without perturbation of insulin sensitivity in hypertriglyceridemic NIDDM patients.

Technical and clinical evaluation of an electrochemistry glucose meter: experience in a diabetes center.

The Sensorex (Metertech, Taipei, Taiwan), an electrochemical blood glucose meter, is designed for self-monitoring of blood glucose (BG) concentrations in capillary blood through the use of an electrochemical test strip. The intra-assay coefficients of variation of Sensorex were 5.2, 5.4, and 4.7% at BG levels of 46, 154 and 302 mg/dl respectively. The BG concentrations tested by Sensorex were correlated well with those by YSI method (r approximately/= 0.85, P < 0.0001). The intraclass correlation coefficients (rI) between the results obtained by Sensorex and YSI were 0.84 in capillary blood and 0.69 in venous whole blood, which indicated good agreement between both methods. The Sensorex was evaluated by error grid analysis and revealed 'acceptance' results. In field test, the Sensorex results obtained by lay users were in concordance with those by trained technicians (rI = 0.87). Our data show that the Sensorex glucometer is reliable and easy to use. We also demonstrate a practical clinical approach for the evaluation of a novel SMBG system.

Increased concentrations of atrial and plasma atrial natriuretic peptide in castrated male rats.

The effects of orchiectomy and testosterone replacement on the plasma concentration and the atrial stores of atrial natriuretic peptide (ANP) were studied in the rats. Male rats were orchiectomized (Orc) three weeks before replacement with testosterone propionate (TP, 20 mg/ml/kg body weight) or sesame oil for five days. Immunoreactive ANP (IR-ANP) in the extracted right atria and plasma of experimental rats was measured. Plasma ANP concentrations were 206 +/- 22, 927 +/- 151, and 264 +/- 61 pg/ml in normal control, Orc, and Orc + TP rats, respectively. ANP contents in right atria were higher in Orc (108 +/- 9 ng/mg tissue) and TP-treated Orc rats (123 +/- 9 ng/mg tissue) than in normal animals (32 +/- 7 ng/mg tissue). These results indicate an increased plasma concentration and atrial stores in the castrated male rats. Replacement of testosterone in the castrated male rats does not decrease the atrial ANP stores, but decreases the plasma ANP concentration.

Using semi-automated oscillometric blood pressure measurement in diabetic patients and their offspring.

To determine whether a semi-automatic oscillometric blood pressure (BP) monitor Dinamap 1846SX (DIN) can replace the standard mercury sphygmomanometer (SMS) for BP measurements in diabetic patients and their offspring, we compared SMS with DIN in 105 diabetic patients and their families. Their mean age was 50.6 (range 24-86) years, of whom 41 had diabetes mellitus (DM), 32 impaired glucose tolerance and 32 non-DM. After resting quietly for 10 min, their right arm BP were measured twice with each device at random and with 1-min intervals between each measurement. Agreement between measurements was tested by plotting the differences between the methods against means and by intraclass correlation coefficient (r(I)). The DIN was also evaluated by the criteria of American Association for the Advancement of Medical Instrumentation (AAMI), the British Hypertension Society (BHS) criteria and clinical criteria of O'Brien. All measurements by DIN [first readings or averaged readings of duplicate measurements of systolic BP (SBP) or diastolic BP (DBP)] satisfied the AAMI criteria and had good agreement with SMS (r(I)=. 951 for SBP and r(I)=.905 for DBP). The first readings of systolic BP measured by DIN vs. SMS failed to satisfy the criteria by O'Brien and reached BHS grade C level. Other measurements passed the limits of O'Brien and reached BHS grade A or B. In conclusion, averaged readings of duplicate BP measurements by DIN are interchangeable with that by SMS in Chinese diabetic patients and their offspring. Only one single DIN measurement is not acceptable for clinical application.

Comparison of official coders versus physician panel in assignment of underlying cause of death.

BACKGROUND AND PURPOSE: In outcome analyses of clinical trials and mortality follow-up studies, the underlying cause of death (UCOD) is commonly assigned either by official coders or by a panel of physicians. We evaluated the validity of UCOD assigned by official coders by comparison with the assignments of a panel of physicians who reviewed the available medical records of the deceased. METHODS: The comparisons focused on deaths occurring from October 1995 through June 1998 in a series of residents in a veterans home. Because of limited resources, only the first 104 deaths that occurred during the study period were included. Agreement rate, sensitivity, specificity, and kappa statistics were calculated to assess the consistency of coder versus physician panel assignment of UCOD by selected main causes of death. For 32 of the 104 deaths, the panel concluded that the information obtained from medical records was insufficient to determine the UCOD, and the following analyses were confined to the other 72 deaths. RESULTS: For the 72 deaths considered by the panel to have sufficient information to determine UCOD, all four physicians agreed on a single UCOD in 50 (69%) cases, while three or four agreed in 66 (92%) cases. A consensus was reached in cases with disagreement. The two procedures completely agreed in 40 (56%) of the deaths. For general category UCOD, the kappa value was high for cancer (0.83) and cardiovascular disease (CVD, 0.73) but only moderate for pulmonary disease (PD, 0.60). When the UCOD assigned by the panel was used as the gold standard, official coders showed relatively low sensitivity for correct determination of UCOD in cases of CVD (0.76) compared with cancer (0.86) and PD (0.80). CONCLUSIONS: Given the high inter-physician consistency and the relatively low sensitivity of official coders in assigning CVD as the UCOD, we conclude that the use of clinical review panels would provide more accurate UCOD assignments for use in outcome analyses in mortality follow-up studies and clinical trials in Taiwan.

Discordant secretions of ACTH and cortisol: an observation indicating multifactoral regulation of adrenal function.

To test the long-standing concept that secretion of adrenal glucocorticoids is solely dependent upon plasma level of adrenocorticotropic hormone (ACTH), we collected sequential blood samples from normal subjects and patients with pituitary-adrenal axis disorders at 30-min intervals for 24 hours and analyzed for both the plasma ACTH and cortisol profiles. In a majority of time points, the changes of cortisol levels coincided with those of ACTH. However, in all individuals tested so far, on more than 24 per cent of occasions, plasma cortisol rose together with a declining or fell with an elevating plasma ACTH level, that indicates a secretory discordance between these two hormones. These discordant patterns cannot be explained simply by the ACTH-stimulatory and cortisol-feedback inhibitory mechanisms. Since a generalized quantitative relationship between the overall profiles of plasma ACTH and cortisol did exist and the mutually regulatory pathways between pituitary and adrenal functions were mostly observable, there were no other known reasons explaining why these frequent and unsynchronized secretory activities should happen. Our observation reveals that cortisol secretion is probably under some other minor but normal influences in addition to the major regulatory action of ACTH.

Undiagnosed diabetes mellitus in Taiwanese subjects with impaired fasting glycemia: impact of female sex, central obesity, and short stature.

AIMS: To study the extent and determinants of undiagnosed diabetes mellitus (DM) in Taiwanese subjects with impaired fasting glycemia (IFG) defined by the newly proposed WHO criteria. METHODS: Oral glucose tolerance tests were carried out for 306 IFG subjects identified from 6632 adult participants of two large scale community-based studies: Nutrition and Health Survey in Taiwan (1993-1996) and the Cardiovascular Disease Two-township Study (1994-1997). Similar protocols were used in these two studies to collect data on glycemic status, anthropometric measurements, and other data used in the present study. RESULTS: Subjects with IFG had a non-trivial undiagnosed diabetes mellitus rate (30% in men and 42% in women) and a high rate of glucose intolerance and undiagnosed DM combined (75% in men and 86% in women). Women with IFG had a 1.6 fold higher risk (p = 0.04) for undiagnosed DM and a 2.1 fold higher risk (p = 0.01) for glucose intolerance and DM when compared to men. There were more women than men with an elevated body mass index in undiagnosed DM patients. Among IFG subjects, undiagnosed DM patients were significantly (p < 0.05) older, more centrally obese and shorter than their normal IFG counterparts, irrespective of gender. In men, height was independent of age and waist circumference in predicting undiagnosed DM (p = 0.037). CONCLUSIONS: A high proportion of impaired glucose tolerance and undiagnosed DM was found in subjects with IFG. Its public health impact should not be overlooked. Central obesity, female sex, and short stature were associated with undiagnosed DM status in IFG subjects.

Regulatory patterns of plasma pituitary-adrenal and pituitary-thyroid hormone secretions: indication for adrenal factor inhibiting adrenal response to ACTH.

Although organization and hormonal regulation of the hypothalamic-pituitary-adrenocortical (HPA) and the hypothalamic-pituitary-thyroid (HPT) axes share a remarkable degree of similarities, distinctive patterns of their plasma hormone secretions are observed. We measured plasma levels of ACTH-cortisol (PA) and hTSH-T3 (PT) pairs of hormones in 24-hour sequential blood specimens sampled at 30-minute intervals from 3 patients with suspected adrenal disorders and 4 normal volunteers and found the same percentage of discordant secretions of the PA and PT hormones but significantly greater coefficients of variations of the PA values than the PT values (p < 0.002). This confirms that plasma PT hormones are more tightly self-regulated between themselves than plasma PA hormones. Moreover, cluster analysis of the 24-hour plasma hormonal fluctuations revealed one or more ACTH-cortisol hyposecretory clusters only in subjects with a normal status of adrenal function. There was no similar hTSH-T3 hyposecretory cluster detected in any one of the 7 subjects. Based on these results, we postulate that there is some adrenal factor normally exerting a subtle antagonistic action against ACTH and causes the incidence of such ACTH-cortisol hyposecretory cluster.

Effect of hypothyroidism on the in vitro release of atrial natriuretic peptide in response to sodium challenge in rats.

The release of atrial natriuretic peptide (ANP) in vitro in response to the challenge of sodium chloride was investigated in hypothyroid rats. Male rats were injected with propylthiouracil (PTU, 20mg/kg BW, intraperitoneally), or PTU and thyroxine (T4, 20 micrograms/kg BW, subcutaneously) once daily for 14 days before decapitation. Rats injected with saline were used as control. The plasma samples were collected and extracted by Sep-Pak C18 cartridge. The concentrations of ANP in extracted plasma were measured by a radioimmunoassay (RIA). PTU-induced hypothyroidism resulted in decreased concentrations of plasma ANP. Replacement of T4 in PTU-treated hypothyroid rats restored the plasma concentrations of ANP to normal levels. Furthermore, we examined the right atrial ANP contents and the in vitro release of ANP in PTU-treated rats and control animals. The right atrium was excised and divided into 5 equal pieces, one was homogenized with 0.1 N HCl and extracted by Sep-Pak C18 immediately, and the others were incubated with Locke's solution at 37 degrees C. After basal incubation for 30 min, rat atrial tissues were then incubated with 154, 160, or 165 mM NaCl for 30 min. The concentrations of ANP in extracted atrial tissue and medium samples were also measured by RIA. Decreased atrial contents of ANP were noted in hypothyroid rats. The in vitro release of ANP in response to 165 mM sodium ion was significantly lower in PTU than in saline-injected animals. These results suggest that lower concentration of plasma ANP in hypothyroid rats is at least in part due to impairment of stimulation-secretion responses of right atria during thyroid hypofunction in rats.