Continuous Glucose Monitoring in Older Adults: What We Know and What We Have Yet to Learn

OBJECTIVE

To assess the growing use of continuous glucose monitoring (CGM) systems by older adults and explore additional areas integration that could benefit adults with frailty.

BACKGROUND

The use of CGM devices has expanded rapidly in the last decade. This has been supported by substantial data showing significant benefit in glycemic metrics: hemoglobin A1c improvements, less hypoglycemia, and improved quality of life. However, sub-populations, such as older persons, exist where available data are limited. Furthermore, frail older adults represent a heterogeneous population with their own unique challenges to the management of diabetes. This group has some of the poorest outcomes related to the sequela of diabetes. For example, hypoglycemia resulting in significant morbidity and mortality is more frequent in older person with diabetes than in younger persons with diabetes.

METHOD

We present a concise literature review on CGM use in the older adult as well as expand upon glycemic and nonglycemic benefits of CGM for patients, caregivers, and providers. Retrospective analysis of inpatient glycemic data of 16,935 older adults with Type 2 diabetes mellitus at Atrium Health Wake Forest Baptist indicated those with fraility managed with insulin or sulfonylurea had the highest rates of delirium (4.8%), hypoglycemia (3.5%), cardiovascular complications (20.2%) and ED visits/hospitalizatoins (49%). In addition, we address special consideration of specific situations including inpatient, palliative and long term care settings.

CONCLUSION

This review article summarizes the available data for CGM use in older adults, discusses the benefits and obstacles with CGM use in this population, and identifies areas of future research needed for improved delivery of care to older persons with diabetes.

Precision nephrotoxicity testing using 3D in vitro models

Nephrotoxicity is a significant concern during the development of new drugs or when assessing the safety of chemicals in consumer products. Traditional methods for testing nephrotoxicity involve animal models or 2D in vitro cell cultures, the latter of which lack the complexity and functionality of the human kidney. 3D in vitro models are created by culturing human primary kidney cells derived from urine in a 3D microenvironment that mimics the fluid shear stresses of the kidney. Thus, 3D in vitro models provide more accurate and reliable predictions of human nephrotoxicity compared to existing 2D models. In this review, we focus on precision nephrotoxicity testing using 3D in vitro models with human autologous urine-derived kidney cells as a promising approach for evaluating drug safety.

A Consensus Statement for Continuous Glucose Monitoring Metrics for Inpatient Clinical Trials

Diabetes Technology Society organized an expert consensus panel to develop metrics for research in the use of continuous glucose monitors (CGMs) in a hospital setting. The experts met virtually in small groups both before and after an April 13, 2023 virtual meeting of the entire panel. The goal of the panel was to develop consensus definitions in anticipation of greater use of CGMs in hospital settings in the future. Establishment of consensus definitions of inpatient analytical metrics will be easier to compare outcomes between studies. Panelists defined terms related to 10 dimensions of measurements related to the use of CGMs including (1) hospital hypoglycemia, (2) hospital hyperglycemia, (3) hospital time in range, (4) hospital glycemic variability, (5) hospital glycemia risk index, (6) accuracy of CGM devices and reference methods for CGMs in the hospital, (7) meaningful time blocks for hospital glycemic goals, (8) hospital CGM data sufficiency, (9) using CGM data for insulin dosing, and (10) miscellaneous factors. The panelists voted on 51 proposed recommendations. Based on the panel vote, 51 recommendations were classified as either strong (43) or mild (8). Additional research is needed on CGM performance in the hospital. This consensus report is intended to support that type of research intended to improve outcomes for hospitalized people with diabetes.

Primary Adrenal Insufficiency due to Cryptococcus With Persistent Adrenal Enlargement and Insufficiency

Background/Objective

Infiltrative fungal infections are an unusual cause of primary adrenal insufficiency (AI). Our objective is to present a long-term follow-up of a patient with AI due to cryptococcal adrenalitis.

Case Report

A 47-year-old woman presented in January 2004, with 50-lb weight loss, nausea, emesis, and headache with diplopia. During the 6 months prior to her presentation the patient had multiple admissions for evaluation of recurrent nausea and emesis. Prior to the most recent of these admissions, the patient developed a headache; evaluation of her cerebrospinal fluid revealed the presence of Cryptococcus, and she was treated with a 2-week course of amphotericin B. Physical examination demonstrated a temperature of 101.1 °F, heart rate of 110 bpm, and blood pressure of 94/65 mm Hg. She appeared ill and was underweight with dry mucous membranes and photophobia. Laboratory tests revealed random cortisol of 0.5 μg per dL. CT imaging showed bilateral adrenal gland enlargement and fine needle aspiration of the adrenal gland revealed encapsulated budding yeast. Stress dose intravenous glucocorticoids were administered and switched to oral hydrocortisone and fludrocortisone because the patient clinically improved with a second course of amphotericin B. Further evaluation in 2017 revealed persistently enlarged adrenal glands, positive cryptococcus antigen, and low IgG levels.

Discussion

Our literature review noted few publications of AI caused by disseminated cryptococcus with no long-term follow-up of these cases beyond a 1- to 4-year time frame.

Conclusion

Patients with AI due to disseminated fungal infection need long-term follow-up to assess for resolution of adrenal enlargement and evaluation of immunocompromised status.

Feasibility of intraoperative continuous glucose monitoring: An observational study in general surgery patients

BACKGROUND

Perioperative hyperglycemia is associated with adverse outcomes in surgical patients, and major societies recommend intraoperative monitoring and treatment targeting glucose <180-200 mg/dL. However, compliance with these recommendations is poor, in part due to fear of unrecognized hypoglycemia. Continuous Glucose Monitors (CGMs) measure interstitial glucose with a subcutaneous electrode and can display the results on a receiver or smartphone. Historically CGMs have not been utilized for surgical patients. We investigated the use of CGM in the perioperative setting compared to current standard practices.

METHOD

This study evaluated the use of Abbott Freestyle Libre 2.0 and/or Dexcom G6 CGMs in a prospective cohort of 94 participants with diabetes mellitus undergoing surgery of ≥3 h duration. CGMs were placed preoperatively and compared to point of care (POC) BG checks obtained by capillary samples analyzed with a NOVA glucometer. Frequency of intraoperative blood glucose measurement was at the discretion of the anesthesia care team, with a recommendation of once per hour targeting BG of 140-180 mg/dL. Of those consented, 18 were excluded due to lost sensor data, surgery cancellation, or rescheduling to a satellite campus resulting in 76 enrolled subjects. There were zero occurrences of failure with sensor application. Paired POC BG and contemporaneous CGM readings were compared with Pearson product-moment correlation coefficients, and Bland-Altman plots.

RESULTS

Data for use of CGM in perioperative period was analyzed for 50 participants with Freestyle Libre 2.0, 20 participants with Dexcom G6, and 6 participants with both devices worn simultaneously. Lost sensor data occurred in 3 participants (15%) wearing Dexcom G6, 10 participants wearing Freestyle Libre 2.0 (20%) and 2 of the participants wearing both devices simultaneously. The overall agreement of the two CGM's utilized had a Pearson correlation coefficient of 0.731 in combined groups with 0.573 in Dexcom arm evaluating 84 matched pairs and 0.771 in Libre arm with 239 matched pairs. Modified Bland-Altman plot of the difference of CGM and POC BG indicated for the overall dataset a bias of -18.27 (SD 32.10).

CONCLUSIONS

Both Dexcom G6 and Freestyle Libre 2.0 CGMs were able to be utilized and functioned well if no sensor error occurred at time of initial warmup. CGM provided more glycemic data and further characterized glycemic trends more than individual BG readings. Required time of CGM warm up was a barrier for intraoperative use as well as unexplained sensor failure. CGMs had a fixed warm of time, 1 h for Libre 2.0 and 2 h for Dexcom G6 CGM, before glycemic data obtainable. Sensor application issues did not occur. It is anticipated that this technology could be used to improve glycemic control in the perioperative setting. Additional studies are needed to evaluate use intraoperatively and assess further if any interference from electrocautery or grounding devices may contribute to initial sensor failure. It may be beneficial in future studies to place CGM during preoperative clinic evaluation the week prior to surgery. Use of CGMs in these settings is feasible and warrants further evaluation of this technology on perioperative glycemic management.

Efficacy of Control-IQ Technology in a General Endocrine Clinic

OBJECTIVE

Recent advances in technology have allowed for the expanded use of hybrid closed-loop insulin pump therapy and automated insulin delivery systems for the management of diabetes mellitus. We assessed the outcomes of introducing Tandem t:slim X2 with the Control-IQ technology in a general endocrine clinic.

METHODS

Data from 66 adults with type 1 (n = 61) and type 2 (n = 5) diabetes mellitus were aggregated for analysis. Patients were either transitioned from traditional insulin pump therapy or multiple daily injection therapy to Tandem t:slim X2 with the Control-IQ technology from January 2020 to June 2021. The assessed clinical end points included changes in time below range, time above range, and time in target range. Changes in hemoglobin A1C before and after Control-IQ technology implementation were noted. The primary outcome was a change in time in target range with the Control-IQ technology.

RESULTS

There was a significant increase in time in target range when comparing pre- and post-Control-IQ technology (49.5% vs 63.3%, P < .0003) values. There was a reduction in time above range (46.8% vs 34.9%, P < .0013), a decrease in time below range (4.0% vs 1.7%, P = .017), and a decrease in hemoglobin A1C after transitioning to the Control-IQ technology (7.7% [61 mmol/mol] vs 7.1% [54 mmol/mol], P < .017). The patient dropout rate was low (7%).

CONCLUSION

The Control-IQ technology system was effective in reducing hyperglycemia while increasing time in target range and decreasing hypoglycemia. This technology is a useful and effective addition to the growing number of automated insulin delivery systems. The clinical outcomes mirror the results found in the key adult pivotal trials.

Real-World Efficacy of the Hybrid Closed-Loop System

BACKGROUND

Hybrid closed-loop (HCL) insulin pump therapy (Medtronic 670G) is an emerging technology that is growing in use worldwide. Initial clinical trials demonstrated the effectiveness of HCL in reducing hypoglycemia and improving glucose control; however, these subjects were intensely monitored and supervised. There has been concern regarding the ability of patients to remain in auto mode. We aimed to assess HCL when used in a typical outpatient endocrine clinic.

METHODS

We initially analyzed data from 80 individuals with type 1 diabetes managed in an endocrine clinic by a single certified diabetes educator (CDE). We then included our other providers and had 230 subjects by the end of the study. Patients were either transitioned from traditional insulin pump or multiple daily insulin injection therapy (MDI) to HCL. Patients initiated to HCL pump therapy from July 2017 through February 2020 were studied. Endpoints of change in time in hypoglycemic/hyperglycemic range and time in target range were analyzed. The primary outcome was a change in percent time in the target range during manual mode compared with auto mode.

RESULTS

There was an 18.2% increase in average time in target range when comparing manual mode to auto mode (59.3% vs 70.1%, P < .0001). Average time in hyperglycemic range was significantly reduced by 26.7% (39.0% vs 28.6%, P < .0001) but without increasing average time in hypoglycemic range (1.7% vs 1.3%, P = 0.95).

CONCLUSIONS

HCL was effective in reducing hyperglycemia and increasing time in the target range but did not increase hypoglycemia. These data suggest HCL will improve the metrics of glucose control.

Telehealth Technologies and Their Benefits to People With Diabetes

This article reviews the current diabetes technology landscape and how recent advancements are being used to help overcome barriers in the management of diabetes. The authors offer case examples of how digital tools and platforms can facilitate diabetes care via telehealth and remote patient monitoring for individuals in special populations. They also provide tips to ensure success in implementing diabetes technology to provide the best possible care for people with diabetes in outpatient settings.

Characteristics and Attitudes of Men Using Anabolic Androgenic Steroids (AAS): A Survey of 2385 Men

Additional characterization of patients using anabolic androgenic steroids (AAS) is needed to improve harm reduction and cessation resources for patients. Our group sought to expand upon the currently limited data regarding AAS use by performing a web-based survey assessing experiences of males using AAS. Participants included men over the age of 18 with history of AAS use within the past 5 years. Data were collected between August 2019 and April 2020. Primary outcome measures included age when starting AAS, dose of AAS, motivations for use, experiences with health-care professionals, and rate of successful cessation. The survey was accessed 3640 times, resulting in 2385 completed surveys meeting the inclusion criteria (68.93% participation rate).

Average participant age was 31.69 ± 10.09 years. Over half of respondents were from the United States (n = 1271, 53.3%). Motives to use AAS included improving appearance (n = 1959, 82.2%), strength gain (n = 1192, 50%), and self-esteem/body image issues (n = 712, 29.87%). Participants rated physicians poorly, regarding knowledge of AAS (4.08 ± 2.23). Most participants did not reveal AAS use to their health-care providers (n = 1338, 56.1%); of those that did, 55.30% (n = 579) reported feeling discriminated against for their use. Of 46.16% (n = 1101) attempting AAS cessation, 60.22% (n = 663) were unsuccessful. Challenges in the management of AAS use include early onset of use, supraphysiologic doses used, and frequently present body image disorders stress. Distrust of health-care providers, poor cessation rates, and lack of physician training further exacerbate this. These findings should serve to reinforce previous calls to action for further research on the treatment of AAS use disorder.

Subcutaneous Insulin Dosing Calculators for Inpatient Glucose Control

PURPOSE OF REVIEW

The goal of this review is to summarize information about insulin dosing software and calculators used as computerized decision support systems or electronic glucose management systems (eGMS). These are used for hospitalized, insulin-treated patients with diabetes. We describe the advantages and disadvantages and the rationale for their use.

RECENT FINDINGS

We compared commercially available insulin dosing software, namely, Glucommander™, EndoTool®, GlucoStabilizer®, and GlucoTab®, in addition to computerized order entry systems that are available in electronic health records. The common feature among these eGMS is their ability to limit occurrences of hypoglycemia while achieving and maintaining patients at target blood glucose level. More research needs to be done examining the efficacy of eGMS in disease-specific states and their benefits and utility in preventing adverse outcomes. Their long-term benefits to health care systems are beginning to emerge in cost-saving benefits and prevention of readmissions.

Impaired Regeneration Potential in Urinary Stem Cells Diagnosed from the Patients with Diabetic Nephropathy

Stem cells present in urine possess regenerative capacity to repair kidney injury. However, the unique characteristics of urinary stem cells (USC) from patients with diabetic nephropathy (d-USC) are unknown. The goal of this study was to investigate stemness properties in cell phenotype and regenerative potential of d-USC, compared to USC from healthy individuals. Methods: Thirty-six urine samples collected from patients (n=12, age range 60-75 years) with diabetic nephropathy (stages 3-4 stage chronic kidney disease [CKD]) were compared with 30 urine samples from healthy age-matched donors (n=10, age range 60-74 years). Results: There were approximately six times as many cells in urine samples from patients with diabetic nephropathy, including twice as many USC clones as healthy donors. However, approximately 70% of d-USC had weaker regenerative capacity as assessed by cell proliferation, less secretion of paracrine factors, weaker telomerase activity, and lower renal tubular epithelial differentiation potential compared to healthy controls. In addition, the levels of inflammatory factors (IL-1β and Cx43) and apoptotic markers (Caspase-3, and TUNEL) were significantly increased in d-USC compared to USC (p<0.01). Protein levels of autophagy marker (LC3-II) and mTOR signaling molecules (p-mTOR/mTOR, p-Raptor/Raptor and p-S6K1) were significantly lower in patient with diabetic nephropathy (p<0.01). Nevertheless, up to 30% of d-USC possessed similar regenerative capacity as USC from healthy donors. Conclusions: Regenerative performance of most d-USC was significantly lower than normal controls. Understanding the specific changes in d-USC regeneration capability will help elucidate the pathobiology of diabetic nephropathy and lead to prevent USC from diabetic insults, recover the stemness function and also identify novel biomarkers to predict progression of this chronic kidney disease.

Comparison of Computer-Guided Versus Standard Insulin Infusion Regimens in Patients With Diabetic Ketoacidosis

BACKGROUND

This study was performed to investigate the efficacy of Glucommander (GM) (Glytec®), a computer-based algorithm versus standard (paper form-based) continuous insulin infusion (CII) in the treatment of patients with diabetic ketoacidosis (DKA).

METHODS

This was a retrospective multicenter study involving 2665 patients with DKA treated with either GM (n = 1750) or standard protocols (n = 915) across 34 institutions in the United States. GM estimates the rate of CII using an insulin sensitivity factor referred to as a "multiplier" that ranges between 0.01 and 0.03. Outcomes of interest were differences in time to resolve DKA (blood glucose [BG] <200 mg/dL and bicarbonate < 18 mmol/L) and number of hypoglycemic events defined as a BG <70 mg/dl.

RESULTS

Treatment with GM was associated with lower rates of hypoglycemia during the time of the insulin drip (12.9% vs 35%, P = .001), faster time to normalization of blood glucose (9.7 ± 8.9 vs 10.97 ± 10.2 hours, P = .0001) and resolution of metabolic acidosis (13.6 ± 11.8 vs 17.3 ± 19.6 hours, P = .0001), and shorter hospital length of stay (3.2 ± 2.9 vs 4.5 ± 4.8 days, P = .01) compared to standard care. Best treatment outcomes were achieved with an initial multiplier of 0.01 and a glucose target range between 120 and 180 mg/dl.

CONCLUSION

The GM algorithm in DKA treatment resulted in lower rates of hypoglycemia and faster DKA resolution over standard paper-based algorithms. Prospective randomized clinical trials comparing the efficacy and cost of computer-based algorithms versus standard CII regimens are warranted.

Tides of change: improving glucometrics in a large multihospital health care system

BACKGROUND

This study explores the relationship between education for inpatient diabetes providers and the utilization of insulin order sets, inpatient glucometrics, and length of stay in a large health care system.

METHODS

The study included patients with and without the diagnosis of diabetes. An education campaign included provider-directed diabetes education administered via online learning modules and in-person presentations by trained individuals. Relationships among provider-attended diabetes education, order set usage, and inpatient glucometrics (hypo- and hyperglycemia) were analyzed, as well as length of stay.

RESULTS

Insulin use knowledge scores for all providers averaged 52%, and improved significantly to 93% (P < .001) by the end of the education intervention period. Likewise utilization of electronic basal-bolus order sets increased from a baseline of 20% for patients receiving insulin to 86% within 6 weeks (P < .01) of introduction of order sets. During the study, the incidence of hypoglycemia and hyperglycemia declined from 1.47% to 1.27% and from 23.21% to 17.80%, respectively. However, these improvements were not sustained beyond the completion of the education campaign.

CONCLUSIONS

Education of diabetes health care providers was provided in a large, multihospital system through the use of online learning modules. Adoption of standardized insulin order sets was associated with an improvement in glucometrics. This educational and quality initiative resulted in overall improvements in insulin knowledge, adherence to recommended order sets, inpatient glucometrics, and patient length of stay. These improvements were not sustained, reinforcing the need for repeated educational interventions for those involved in providing inpatient diabetes care.

Improvement in inpatient glycemic care: pathways to quality

The management of inpatient hyperglycemia is a focus of quality improvement projects across many hospital systems while remaining a point of controversy among clinicians. The association of inpatient hyperglycemia with suboptimal hospital outcomes is accepted by clinical care teams; however, the clear benefits of targeting hyperglycemia as a mechanism to improve hospital outcomes remain contentious. Glycemic management is also frequently confused with efforts aimed at intensive glucose control, further adding to the confusion. Nonetheless, several regulatory agencies assign quality rankings based on attaining specified glycemic targets for selected groups of patients (Surgical Care Improvement Project (SCIP) measures). The current paper reviews the data supporting the benefits associated with inpatient glycemic control projects, the components of a successful glycemic control intervention, and utilization of the electronic medical record in implementing an inpatient glycemic control project.

Recombinant human parathyroid hormone therapy (1-34) in an adult patient with a gain-of-function mutation in the calcium-sensing receptor-a case report

OBJECTIVE

To describe a case of hypocalcemia in a patient with a gain-of-function mutation in the calcium-sensing receptor that was undetected until adulthood and successfully treated with recombinant parathyroid hormone.

METHODS

The clinical findings, laboratory data, and a review of the pertinent literature are presented.

RESULTS

A 55-year-old woman was hospitalized and seen by the endocrinology consult service for hypocalcemia that was refractory to repeated doses of intravenous calcium gluconate. She expressed concern about chronic leg muscle cramps and paresthesias of the lips and fingertips. In addition, she had no history of neck surgery, neck irradiation, or any autoimmune disease. She was a well-appearing female with no dysmorphic features or skin changes. Laboratory tests revealed hypocalcemia, hyperphosphatemia, hypomagnesemia, and hypovitaminosis D. Her parathyroid hormone concentration (PTH) was low at 14.2 pg/mL. Her PTH and calcium concentrations remained low despite repletion of magnesium and treatment with calcitriol and oral calcium replacement. A 24-hour collection for urinary calcium showed inappropriate hypercalciuria. Medical records showed her hypocalcemia to be chronic. Additionally, several family members had also complained of muscle cramps. A congenital cause of her hypoparathyroidism was considered, and genetic testing confirmed heterozygosity for a gain-of-function mutation in the calcium-sensing receptor gene associated with autosomal dominant familial isolated hypoparathyroidism (ADH). Treatment with subcutaneous recombinant human parathyroid hormone teriparatide (rhPTH [1-34]) 20 mcg twice daily for three days normalized her calcium and phosphorus concentrations.

CONCLUSION

rhPTH (1-34) is an effective treatment for patients with hypoparathyroidism due to gain-of-function mutations in the calcium-sensing receptor. ADH can be insidious in presentation and the diagnosis can be missed unless there is a high index of suspicion.

The nurse and the use of narrative: an approach to caring

The use by the nurse of the principles of narrative therapy to help patients re-author their personal narrative, and change it from a problem-saturated story to one that is more preferred, is explored. Three main narrative techniques: deconstruction, externalization and re-authoring are described. Examples of these techniques are provided to help nurses at all levels of nursing practice assume the role of collaborator in the re-authoring process.

Nursing the disenfranchised: women who have relinquished an infant for adoption

Grief that occurs as a result of relinquishing an infant for adoption is explored. Traditional grief models are cited as ineffectual for the satisfactory resolution of grief resulting from the relinquishment of a child for adoption. The reasons for disenfranchised grief are described and narratives of personal interviews provide insight into the grief process of birthmothers and evidence of their disenfranchisement. The role of psychiatric-mental health nurse is discussed and interventions aimed at assisting the birthmother to grieve are suggested.

Fasting suppresses pulsatile luteinizing hormone (LH) secretion and enhances orderliness of LH release in young but not older men

Pulsatile gonadotropin secretion and sex-steroid concentrations are suppressed reversibly in young fasted or malnourished human subjects. In this study, we investigated the impact of age on the dynamic neuroendocrine mechanisms underlying this stress response in healthy young (age, 28 +/- 3 yr, n = 8) vs. older (age 67 +/- 2 yr, n = 8) men with similar body mass indices (mean, 26 +/- 0.6 vs. 26 +/- 1.3 kg/m2, respectively). Serum LH concentrations were measured by immunoradiometric assay (IRMA) in blood collected at 10-min intervals over 27 h on a control (fed) day and on the third day of a 3.5-day fast (water only) assigned in randomized order. After 24 h of basal sampling, GnRH (10 micrograms i.v. bolus) was administered to test gonadotrope responsiveness. Cortisol, dehydroepiandrosterone sulfate, androstenedione, testosterone, FSH, GH, and PRL were measured in 24-h pooled serum as positive and negative control hormones. Approximate entropy was used to quantitate the orderliness of LH release over 24 h, and a multiple-parameter deconvolution method was applied to quantify pulsatile LH secretion and LH half-life. In the fed state, older men exhibited elevated mean (24-h pooled) serum FSH and cortisol concentrations compared with young controls but equivalent serum LH concentrations and reduced serum GH, free testosterone, androstenedione, and dehydroepiandrosterone sulfate concentrations. Fed older men also manifested a lower frequency and amplitude of 24-h pulsatile LH secretion, and, by approximate entropy calculations, a more disorderly pattern of basal LH release than younger individuals. Three- and one-half days of fasting evoked 40% and 47% increases in mean (24-h) serum cortisol concentrations in young and older men, respectively (P < 0.01 vs. fed, but P = not significant for percentage rise in older vs. young men). Concurrently, fasting induced a 2.1-fold fall in the 24-h endogenous LH production rate in young men (fed 36 +/- 9.7 vs. fasted 17 +/- 2.0 IU/L of distribution volume/day, P < 0.01), but did not significantly affect the daily LH secretion rate in older men (fed 27 +/- 4.5 vs. fasted 21 +/- 3.4 IU/day). The reduced LH production rate in fasting young men was accounted for by a 1.7-fold decline in the mass of LH secreted per burst (fed 2.5 +/- 0.45 vs. fasted 1.5 +/- 0.16 IU/L, P < 0.05), whereas LH burst mass in older men remained unchanged (and low) during fasting. In addition, in young men, during the 3.5-day fast the number of computer-resolved LH secretory bursts per 24 h decreased (fed 15 +/- 0.7 vs. fasted 11 +/- 0.7, P < 0.01), and the interburst interval increased (fed 94 +/- 4.2 vs. fasted 125 +/- 8.7 min, P < 0.05). In contrast, in older men in the fed state, basal LH peak frequency and serum free testosterone concentrations were reduced compared with corresponding values in young men, and did not decline further with fasting. Whereas the orderliness of LH release patterns increased significantly during fasting in the young men, the approximate entropy measure failed to change significantly in unfed older subjects. By cosinor analysis, young men showed lower 24-h mesor (mean of nyctohemeral rhythm of) serum LH concentrations than older volunteers during fasting. Moreover, young but not older men manifested preserved 24-h variations in LH interpulse intervals when fasting. Exogenously stimulated LH release (mean 3-h serum LH concentration or calculated mass of LH secreted) following a single i.v. injection of 10 micrograms GnRH was independent of age and fasting status. We conclude that the metabolic stressor of short-term fasting unmasks specific age-related neuroendocrine contrasts in the stress-responsive control of both the pulsatile and nyctohemeral regulation of the male hypothalamo-pituitary-gonadal-axis.

Polycystic ovary syndrome: evidence for reduced sensitivity of the gonadotropin-releasing hormone pulse generator to inhibition by estradiol and progesterone

Plasma LH is commonly elevated in women with the polycystic ovary syndrome (PCOS), but the underlying mechanisms are uncertain. We tested the hypothesis that the elevated LH in part reflects a reduced sensitivity of the hypothalamic GnRH pulse generator to suppression by estradiol (E2) and progesterone (P). In an initial protocol, normal controls (beginning on cycle days 8-10) and women with PCOS were given E2 transdermally and P by vaginal suppository (three times daily), to achieve plasma concentrations similar to those in the midluteal phase of an ovulatory cycle, for 21 days. Blood was obtained at 10-min intervals for 12 h before and on days 5, 10, 20, and 28 (7 days after E2 and P were discontinued). LH pulse amplitude and LH pulse frequency were suppressed in both PCOS and normal controls, but LH pulse frequency fell more rapidly in controls and was lower by day 10 (P < 0.05). Based on this time course a dose-response study was performed, in which E2 in constant dosage and varying concentrations of P were administered for 7 days. Pulsatile LH release was appraised on days 1 and 7. The frequency of LH pulse secretion was reduced in controls and was lower than that in patients with PCOS on day 7 (P < 0.0001). Plasma P concentrations of 13-15 ng/mL suppressed LH pulse frequency to a similar degree in PCOS and controls. In contrast, lower concentrations (P < 10 ng/mL) were more effective in suppressing GnRH/LH pulse frequency in controls (by > 45% of basal) than in PCOS (< 40%; P < 0.01). The data indicate that E2 and P can inhibit the activity of the hypothalamic GnRH pulse generator in women with PCOS. However, higher plasma concentrations of P were required to reduce GnRH/LH pulse frequency in PCOS compared to controls, suggesting an insensitivity of the GnRH pulse generator to suppression by E2 and P. These results suggest that an abnormality in the regulation of hypothalamic GnRH secretion is present in PCOS and may be a factor in the etiology of the disorder in adolescence.

Ovarian activin receptor subtype and follistatin gene expression in rats: reciprocal regulation by gonadotropins

The production of activin, follistatin (FS), and inhibin, proteins present in the ovary and involved in mammalian reproduction, is regulated by gonadotropins and estradiol. We report here gonadotropin regulation of ovarian activin receptor (ActR) subtype and FS mRNAs. Expression of ActRI, ActRIIA, ActRIIB, and FS mRNA was measured on the afternoon of proestrus (1800 h) and the morning of estrus (0800 h). ActRI and ActIIA subtype mRNA concentrations fell by approximately 50% (p < 0.05) following the proestrous gonadotropin surge (ActRIIB mRNA was undetectable), while FS mRNA was unchanged. To define the contribution of gonadotropins, hypophysectomized (HYPOX) female rats were given recombinant human (rh) FSH and hCG, which decreased both ActR mRNAs (by approximately 70% and aproximately 50% for ActRI and IIA, respectively) and increased FS mRNA by 2-fold. As gonadotropins could act via estradiol (E2), HYPOX rats were given E2; ActRI was decreased, but ActRIIA mRNA was increased. The actions of gonadotropins were preferential, as the combination of rhFSH and hCG with E2 reduced ActRIIA mRNA. FS mRNA was increased to a similar degree by E2 and/or gonadotropins. These data suggest that gonadotropins regulate ActR and FS gene expression via multiple mechanisms. Both a direct action on ActRIIA (inhibition) and an indirect action through E2 on ActRI (inhibition) and FS (stimulation) suggest potential physiologic mechanisms for the reciprocal regulation of ActR subtype and FS mRNAs.

Pulsatile intravenous gonadotropin-releasing hormone administration averts fasting-induced hypogonadotropism and hypoandrogenemia in healthy, normal weight men

Fasting or severe caloric restriction in the human or experimental animal suppresses serum LH and sex steroid concentrations. In healthy men undergoing prolonged (5-day) nutrient deprivation, the daily LH secretion rate, the mass of LH secreted per burst, and the serum testosterone concentration fall markedly, with no decrease in responsiveness to a single bolus of GnRH. Here we test the hypothesis that the hypogonadotropic hypoandrogenemia accompanying fasting reflects decreased endogenous GnRH release. To this end, six healthy young men were studied on a fed day and during two 83-h fasting sessions with concurrent saline or pulsatile GnRH administration (100 ng/kg, i.v., every 90 min for 24 h) followed by a single bolus of 10 microg GnRH, i.v., to evaluate pituitary responsiveness. We employed a highly sensitive LH immunoradiometric assay, which correlates well with an in vitro Leydig cell bioassay, and deconvolution analysis to calculate in vivo LH secretory burst frequency, amplitude, duration, mass, and LH half-life. Fasting resulted in 30-50% declines in serum total and free testosterone and LH concentrations, and a 3-fold decrease in the calculated 24-h LH secretion rate (fed, 42 +/- 12; fasting, 14 +/- 1.9 U/L distribution volume x day; mean +/- SEM; P < 0.05, by ANOVA). Reduced LH secretion was accounted for by dual mechanisms, viz. a fall in both the apparent number of computer-resolved LH secretory bursts per 24 h (fed, 16 +/- 1.1; fasting, 10 +/- 1.2; P < 0.01) and the mass of LH secreted per burst (fed, 2.5 +/- 0.5; fasting, 1.5 +/- 0.1 U/L; P < 0.05). Fasting also decreased the mean value of the 24-h (nyctohemeral) rhythm in serum LH concentrations and reduced the approximate entropy (disorderliness) of LH release. Exogenous pulsatile GnRH injections prevented both the reduction in the calculated daily LH secretion rate (fed, 42 +/- 12; fasting plus GnRH, 64 +/- 16 IU/L; P = NS) and the decline in serum testosterone concentrations (fed, 556 +/- 71 ng/dL; fasting, 391 +/- 41; fasting plus GnRH, 859 +/- 65). Pulsatile GnRH treatment also restored the nyctohemeral mesor of serum LH concentrations and the approximate entropy value to baseline. Administration of a submaximal dose of exogenous GnRH (10 microg, i.v.) at the end of the fasting interval revealed statistically identical LH release in the three study groups, suggesting that pituitary responsiveness to GnRH was unchanged in this paradigm. In summary, a pulsatile iv GnRH infusion in young men averts completely the fasting-induced decline in LH secretory burst mass/amplitude and frequency, reinstates serum total and free testosterone concentrations, and restores the mesor of LH's nyctohemeral rhythmicity and the approximate entropy of LH release. Rescue of hypogonadism by pulsatile GnRH stimuli supports the thesis that nutrient withdrawal decreases the output of the human hypothalamic GnRH burst generator.

Evaluation of amenorrhea

This article has focused on the evaluation of amenorrhea. Primary amenorrhea shares some diagnostic considerations with secondary amenorrhea. Having excluded these diagnostic considerations (pregnancy), the patient with primary amenorrhea should be further evaluated in consultation with an endocrinologist. Secondary amenorrhea is a common clinical complaint and an algorithm is proposed to guide the physician through the diagnostic evaluation. The evaluation is centered around excluding significant pathology in the central nervous system and evaluating for the common gynecological disorder of chronic anovulation. The clinical disorders of PCOS and hyperprolactinemia were discussed briefly, and the interested reader may obtain further information from the authors referenced in this article.

Ovarian inhibin subunit gene expression: regulation by gonadotropins and estradiol

Inhibin and FSH maintain a dynamic inverse relationship throughout the rat estrous cycle. In particular, inhibin alpha- and beta A-subunit messenger RNAs (mRNAs) have been shown to be maximally expressed immediately after the midcycle gonadotropin surge, when both circulating estradiol (E2) and inhibin are also elevated. The current study was designed to investigate the regulation of inhibin subunit gene expression and secretion in vivo by recombinant human FSH (rhFSH) and estradiol. Initially, we determined if physiological levels of rhFSH regulated ovarian inhibin subunit gene expression and secretion. Hypophysectomized (HYPOX) adult female rats received hCG (10 IU, sc) and were then treated for 24 h with either rhFSH (0.5-20 IU every 6 h, i.v.) or saline. Hypophysectomy reduced inhibin subunit mRNAs as well as serum inhibin and estradiol. Although 0.5 IU rhFSH was ineffective in increasing inhibin subunit mRNAs, all doses between 2.5-20 IU increased inhibin subunit gene expression and inhibin secretion. Inhibin alpha-, beta A-, and beta B-subunit mRNAs were increased to a similar degree (3- to 5-fold) by all rhFSH doses of 5 IU or more. Similarly, serum E2 and inhibin were increased 2- and 3-fold, respectively, above HYPOX values after all doses of rhFSH of 5 IU or more. To investigate the role of a pure FSH signal in a physiological dose on inhibin subunit gene expression, HYPOX rats were given either rhFSH (5 IU, i.v., every 6 h for 24 or 48 h), hCG (10 IU, sc), or their combination. Neither gonadotropin when given alone altered inhibin subunit gene expression or serum E2 concentrations. Inhibin secretion rose in response to rhFSH alone, but not to hCG. The combination of hCG and rhFSH resulted in increased inhibin subunit mRNAs (3- to 5-fold) as well as circulating E2 and inhibin concentrations. We next studied the effects of E2 replacement in HYPOX rats at both physiological (serum approximately equal to 40 pg/ml) and higher doses (serum approximately equal to 800 pg/ml, to mimic intraovarian concentrations) in the presence or absence of exogenous gonadotropins (for 24 and 48 h). Although not as effective as gonadotropins, both E2 regimens increased inhibin alpha to a similar degree (2-fold), whereas beta-subunit mRNAs were unchanged at 24 h. Serum inhibin concentrations were increased only 48 h after high dose E2 treatments. As the actions of E2 and gonadotropins on alpha-subunit mRNA were not additive, E2 appears to mediate gonadotropin regulation of alpha-subunit gene expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuroendocrine responses to a novel growth hormone secretagogue, L-692,429, in healthy older subjects

L-692,429 (L), a novel nonpeptide mimic of GH-releasing peptide (GHRP), is a potent GH secretagogue in animals and young men. To assess the safety and efficacy of L in stimulating GH release in healthy older men and women, 16 subjects were admitted to a randomized, double blind, cross-over comparison of i.v. administered placebo, GH-releasing hormone [GHRH-(1-29)-NH2; 1 microgram/kg] and two doses of L (0.2 and 0.75 mg/kg). Blood samples were obtained at 5-min intervals for 60 min before and 240 min after each dose for measurement of GH; cortisol, PRL, and insulin-like growth factor-I (IGF-I) were measured less frequently. Peak and integrated GH concentrations increased significantly after L in a dose-dependent manner. Responses to L at either dose were significantly greater than the response to GHRH: peak GH responses in older men and women were (mean +/- SE; micrograms per L): after placebo, 1.2 +/- 0.2; L (0.2 mg/kg), 16.5 +/- 1.8; L (0.75 mg/kg), 32.2 +/- 3.9; and GHRH, 7.6 +/- 1.3 (P < 0.05, L vs. placebo or GHRH). Serum cortisol and PRL concentrations increased after both doses of L, but to values within the respective normal ranges. Serum IGF-I values did not change consistently in any group. The GH responses to GHRH and L (0.75 mg/kg) were highly correlated (r2 = 0.61; P < 0.0004). Deconvolution analysis demonstrated that the increase in serum GH concentrations stimulated by L and GHRH resulted from enhanced GH secretion rates, with no change in the half-life of GH disappearance. Amplitudes of GH secretory pulses were increased 11-, 18-, and 4-fold after L (0.2 mg/kg), L (0.75 mg/kg), and GHRH treatments, respectively. The number of GH secretory pulses was significantly increased by L (0.75 mg/kg; 4.6 +/- 0.4) and GHRH (4.4 +/- 0.3) compared to placebo (2.6 +/- 0.5), but the interval between pulses was shorter after L (0.75 mg/kg; 28.6 +/- 3.6 min) than after GHRH (50.7 +/- 7.7 min; P < 0.05). Adverse experiences were limited to brief episodes of flushing or a warm sensation about the upper body. L-692,429 is a potent GH secretagogue that is well tolerated in healthy older men and women. At the doses employed in this study, L elicited greater increases in GH secretion rates and serum GH concentrations than GHRH. L-692,429 may have therapeutic advantages over peptide GH secretagogues to restore endogenous GH secretion in GH deficiency states or the hyposomatotropism of aging.

Plasma cortisol and catecholamine responses to intracerebroventricular administration of CRF to rhesus monkeys

Synthetic ovine corticotropin releasing factor (CRF) was administered directly into the 4th ventricle of rhesus monkeys. A dose dependent increase in plasma cortisol was observed following 10 micrograms/kg, 20 micrograms/kg, and 60 micrograms/kg of CRF. Increases in plasma epinephrine were also evident following the highest dose of CRF. Plasma norepinephrine, mean arterial pressure, and heart rate did not increase significantly following CRF administration. These data suggest that in the rhesus monkey, central administration of ovine CRF leads to activation of the pituitary-adrenocortical axis at doses that do not raise plasma catecholamines.

Neuroendocrine and behavioral effects of m-chlorophenylpiperazine administration in rhesus monkeys

The effects of m-chlorophenylpiperazine (mCPP), a serotonin receptor agonist, on the release of plasma prolactin (PRL), growth hormone (GH), and cortisol in the rhesus monkey were studied. mCPP was administered intravenously at doses of 0.5, 1.5, and 3.0 mg/kg. GH and cortisol were increased significantly at all doses while PRL was significantly increased only following administration of 3.0 mg/kg mCPP. mCPP administration also produced behavioral alterations in each monkey, including sedation, penile erection, and defecation. PRL, GH and behavioral responses to mCPP were completely blocked by pretreatment with the serotonin antagonist metergoline (MTG). However, pretreatment treatment with MTG failed to entirely anagonize the cortisol response to mCPP. These data suggest that mCPP has prominent neuroendocrine and behavioral effects which are mediated, in part, by serotonergic mechanisms.

Growth hormone response to clonidine as a probe of noradrenergic receptor responsiveness in affective disorder patients and controls

The growth hormone (GH) response to the alpha-adrenergic agonist clinidine was blunted in 19 depressed patients compared to 20 controls. The difference remained significant when age- and sex-matches pairs of patients and controls were compared from this sample, either including or excluding subjects with elevated GH baseline levels. Plasma levels of free 3-methoxy-4-hydroxyphenyl-glycol (MHPG) were assayed in blood samples drawn just before the clonidine infusion. A modest negative correlation was found between the plasma MHPG values and the magnitude of the GH responses to clonidine, although baseline plasma MHPG levels were not significantly different between patients and controls. The diminished GH response to clonidine observed suggests that many depressed patients may have decreased alpha-adrenoreceptor responsiveness. Decreased responsiveness may in some cases be associated with relatively increased indices of presynaptic noradrenergic availability. Such a model might have implications for understanding the functional status of the noradrenergic neurotransmitter system in depressed patients and the possible subtyping of affective disorder patients.