Impairment of counterregulatory hormone responses to hypoglycemia in pregnant women with insulin-dependent diabetes mellitus

Hypoglycemic unawareness: challenges, triggers, and recommendations in patients with hypoglycemic unawareness: a case report

Background

Hypoglycemia is a fairly common complication in diabetic patients, particularly in those on insulin therapy. Hypoglycemia symptoms are classified into two types: autonomic and neuroglycopenic symptoms. If a person develops neuroglycopenic symptoms before the appearance of autonomic symptoms or is asymptomatic until blood sugar levels are very low, the patient will develop hypoglycemic unawareness (HU).

Case presentation

A 25-year-old Iranian woman with HU presented with a severe hypoglycemic episode. This episode was characterized by loss of consciousness and focal neural deficits, which were unusual symptoms in the patient, who was a medical intern with type 1 diabetes and currently being treated with regular and NPH insulin.

Conclusions

Hypoglycemia is a common complication in diabetic patients receiving oral or insulin therapy. A patient who is unaware of their condition may experience severe and potentially fatal episodes. These incidents can negatively affect their daily lives as well as their careers and jobs. Hypoglycemia-associated autonomic failure is a possible cause for patients with multiple episodes of severe hypoglycemia. IThe use of a continuous glucose monitoring device with an alarm, if available, can be an excellent option for these patients.

Impaired awareness of hypoglycaemia in women with type 1 diabetes in pregnancy: Hypoglycaemia fear, glycaemic and pregnancy outcomes

AIMS

To examine maternal fear of hypoglycaemia, glycaemia and pregnancy outcomes in women with impaired and normal awareness of hypoglycaemia.

METHODS

A pre-planned sub-study of 214 pregnant women with type 1 diabetes who participated in the CONCEPTT trial. Participants completed hypoglycaemia fear surveys (HFS-II) at baseline. Logistic regression and Poisson regression analyses were used to obtain an adjusted estimate for the rate ratio relating awareness to the number of severe hypoglycaemic episodes, and for several neonatal outcomes in relation to the total HFS-II score. The role of continuous glucose monitoring (CGM) use was examined.

RESULTS

Overall, 30% of participants reported impaired awareness of hypoglycaemia (n = 64). Women with impaired awareness of hypoglycaemia had more episodes of severe hypoglycaemia (mean 0.44 vs. 0.08, p < 0.001) (12-34 weeks gestation) and scored higher on the HFS-II scale (43.7 vs. 36.0, p 0.008), indicating more fear of hypoglycaemia. They spent more time below range (CGM <3.5 mmol/L) and exhibited more glycaemic variability at 12 weeks gestation. Higher overall HFS-II scores were associated with a higher risk of maternal severe hypoglycaemia episodes (Rate Ratio 1.78, 95% CI 1.39-2.27). Women with impaired awareness of hypoglycaemia had less maternal weight gain but there were no differences in neonatal outcomes between women with impaired awareness of hypoglycaemia and normal hypoglycaemia awareness. Higher HFS-II scores were associated with more nephropathy (Odds Ratio 1.91, 95% CI 1.06-3.4). CGM use after 12 weeks was not associated with the number of episodes of severe hypoglycaemia (RR 0.75, 95% CI 0.49-1.15; p = 0.18).

CONCLUSIONS

In pregnant women with type 1 diabetes, impaired awareness of hypoglycaemia is associated with more maternal severe hypoglycaemia episodes and more fear of hypoglycaemia. Having impaired awareness of hypoglycaemia and/or fear of hypoglycaemia should alert clinicians to this increased risk. Reassuringly, there was no increase in adverse neonatal outcomes.

Hypoglycaemia

In health hypoglycaemia is rare and occurs only in circumstances like extreme sports. Hypoglycaemia in type 1 Diabetes (T1D) and advanced type 2 Diabetes (T2D) are the result of interplay between absolute or relative insulin access and defective glucose counterregulation. The basic mechanism is, failure of decreasing insulin and failure of the compensatory increasing counterregulatory hormones at the background of falling blood glucose. Any person with Diabetes on anti-diabetic medication who behaves oddly in any way whatsoever is hypoglycaemic until proven otherwise. Hypoglycaemia can be a terrifying experience for a patient with Diabetes. By definition, hypoglycaemic symptoms are subjective and vary from person to person and even episode to episode in same person. Fear of iatrogenic hypoglycaemia is a major barrier in achieving optimum glycaemic control and quality of life which limits the reduction of diabetic complications. Diabetes patients with comorbidities especially with chronic renal failure, hepatic dysfunction, major limb amputation, terminal illness, cognitive dysfunction etc. are more vulnerable to hypoglycaemia. In most cases, prompt glucose intake reverts hypoglycaemia. Exogenous insulin in T1D and insulin treated advanced T2D have no control by pancreatic regulation. Moreover, failure of increase of glucagon and attenuated secretion in epinephrine causes the defective glucose counterregulation. In this comprehensive review, I will try to touch all related topics for better understanding of hypoglycaemia.

The fetal circadian rhythm in pregnancies complicated by pregestational diabetes is altered by maternal glycemic control and the morning cortisol concentration

Circadian rhythmicity is fundamental to human physiology, and is present even during fetal life in normal pregnancies. The impact of maternal endocrine disease on the fetal circadian rhythm is not well understood. The present study aimed to determine the fetal circadian rhythm in pregnancies complicated by pregestational diabetes mellitus (PGDM), compare it with a low-risk reference population, and identify the effects of maternal glycemic control and morning cortisol concentrations. Long-term fetal electrocardiogram recordings were made in 40 women with PGDM at 28 and 36 weeks of gestation. Two recordings were made in 18 of the women (45.0%) and one recording was made in 22 (55.0%). The mean fetal heart rate (fHR) and the fHR variation (root mean square of squared differences) were extracted in 1-min epochs, and circadian rhythmicity was detected by cosinor analysis. The study cohort was divided based on HbA1c levels and morning cortisol concentrations. Statistically, significant circadian rhythms in the fHR and the fHR variation were found in 45 (100%) and 44 (95.7%) of the 45 acceptable PGDM recordings, respectively. The rhythms were similar to those of the reference population. However, there was no statistically significant population-mean rhythm in the fHR among PGDM pregnancies at 36 weeks, indicating an increased interindividual variation. The group with higher HbA1c levels (>6.0%) had no significant population-mean fHR rhythm at 28 or 36 weeks, and no significant fHR-variation rhythm at 36 weeks. Similarly, the group with a lower morning cortisol concentration (≤8.8 µg/dl) had no significant population-mean fHR-variation rhythm at 28 and 36 weeks. These findings indicate that individual fetal rhythmicity is present in pregnancies complicated by PGDM. However, suboptimal maternal glycemic control and a lower maternal morning cortisol concentration are associated with a less-well-synchronized circadian system of the fetus.

The Impact of Pregnancy and Parity on Type 1 Diabetes Complications

BACKGROUND

The potential influence of pregnancy and parity on the risk of chronic diabetic complications is a matter of great concern and constant discussion. This aspect seems relevant and should be the subject of thorough discussion with the woman planning childbirth.

INTRODUCTION

Current data concerning the impact of pregnancy and parity covers primarily retinopathy and nephropathy, while the aspects of neuropathy and macrovascular complications are unsatisfactorily documented. Majority of studies focus on single complication only, while the number of papers assessing this problem in a complex setting is limited. The available body of evidence concerns mainly the short-term impact of pregnancy on diabetic chronic complications while the data concerning the longer perspective are scarce. Moreover, the results found in the available literature are conflicting. The aim of the study was to summarize all available data concerning the longer impact of parity on the chronic complications in the women with type 1 diabetes.

METHODS

PubMed database has been searched between October 2013 and September 2018 and all relevant papers were selected. This review summarizes data on the impact of pregnancy and parity on chronic complications in type 1 diabetic women.

RESULTS

Current data assessing this matter in a complex way are limited, and the available results are controversial. It seems however that pregnancy itself may rather influence pre-existing diabetic complication than affect risk of its development. Additionally, evidence suggests that any deleterious changes appearing during pregnancy are transient and tend to remit after delivery.

CONCLUSION

It seems that neither pregnancy nor parity affects the risk of diabetic chronic complications in the longer perspective.

Masked hypoglycemia in pregnancy

BACKGROUND

Hypoglycemia is a major hindrance for optimal glycemic control in women with gestational diabetes mellitus (GDM) on insulin. In the present study, masked hypoglycemia (glucose <2.77mmol/L for ≥30 min) was estimated in pregnant women using a continuous glucose monitoring (CGM) system.

METHODS

Twenty pregnant women with GDM on insulin (cases) and 10 age-matched euglycemic pregnant women (controls) between 24 and 36 weeks gestation were recruited. Both groups performed self-monitoring of blood glucose (SMBG) and underwent CGM for 72 h to assess masked hypoglycemia. Masked hypoglycemic episodes were further stratified into two groups based on interstitial glucose (2.28-2.77 and ≤2.22 mmol/L).

RESULTS

Masked hypoglycemia was recorded in 35% (7/20) of cases and 40% (4/10) of controls using CGM, with an average of 1.28 and 1.25 episodes per subject, respectively. Time spent at glucose levels between 2.28 and 2.77 mmol/L did not differ between the two groups (mean 114 vs 90 min; P = 0.617), but cases spent a longer time with glucose ≤2.2 mmol/L. Babies born to women with GDM were significantly lighter than those born to controls (2860 vs 3290 g; P = 0.012). There was no significant difference in birth weight within the groups among babies born to women with or without hypoglycemia.

CONCLUSION

Euglycemic pregnant women and those with GDM on insulin had masked hypoglycemia. Masked hypoglycemia was not associated with adverse maternal or fetal outcomes. Therefore, low glucose levels in the hypoglycemic range may represent a physiologic adaptation in pregnancy. This response is exaggerated in women with GDM on insulin.

Pregnancy Outcomes in Women With Diabetes-Lessons Learned From Clinical Research: The 2015 Norbert Freinkel Award Lecture

Among women with diabetes, the worst pregnancy outcome is seen in the subgroup of women with diabetic nephropathy. Development of severe preeclampsia that leads to early preterm delivery is frequent. Predictors and pathophysiological mechanisms for the development of preeclampsia among women with diabetes and observational studies that support antihypertension treatment for pregnant women with microalbuminuria or diabetic nephropathy preventing preeclampsia and early preterm delivery are presented here. Obtaining and maintaining strict glycemic control before and during pregnancy is paramount to prevent preterm delivery. The cornerstones of diabetes management are appropriate diet and insulin, although the risk of severe hypoglycemia always needs to be taken into account when tailoring a diabetes treatment plan. Pathophysiological mechanisms of the increased risk of hypoglycemia during pregnancy are explored, and studies evaluating the use of insulin analogs, insulin pumps, and continuous glucose monitoring to improve pregnancy outcomes and to reduce the risk of severe hypoglycemia in pregnant women with type 1 diabetes are reported. In addition to strict glycemic control, other factors involved in fetal overgrowth are explored, and restricting maternal gestational weight gain is a promising treatment area. The optimal carbohydrate content of the diet is discussed. In summary, the lessons learned from this clinical research are that glycemic control, gestational weight gain, and antihypertension treatment all are of importance for improving pregnancy outcomes in pregnant women with preexisting diabetes. An example of how to use app technology to share the recent evidence-based clinical recommendations for women with diabetes who are pregnant or planning pregnancy is given.

Impaired hormonal counterregulation to biochemical hypoglycaemia does not explain the high incidence of severe hypoglycaemia during pregnancy in women with type 1 diabetes

AIMS

To explore hormonal counterregulation to biochemical hypoglycaemia during pregnancy.

METHODS

Observational study of 107 consecutive pregnant women with type 1 diabetes (median duration 16 years (range 1-36), HbA1c 6.6% (4.9-10.5) in early pregnancy) and 22 healthy pregnant women. At 8, 14, 21, 27 and 33 weeks (women with diabetes) and 15, 28 and 34 weeks (healthy women) blood was sampled for measurements of glucose, adrenaline, noradrenaline, cortisol and glucagon. Each woman's measurement of serum glucose was matched with her corresponding hormone concentrations. Severe hypoglycaemia (requiring help from another person) was recorded prospectively.

RESULTS

During normoglycaemia (serum glucose > 3.9 mmol/L), adrenaline concentrations were higher in early pregnancy compared with late pregnancy in women with diabetes (21 (7-111) pg/ml vs. 17 (2-131), p = 0.02) and healthy women (21 (10-37) pg/ml vs. 13 (5-49), p = 0.046). Biochemical hypoglycaemia (serum glucose ≤ 3.9 mmol/L) occurred in 70 women with diabetes (65%) in at least one of the five samplings. At 8 and 33 weeks, adrenaline concentrations at biochemical hypoglycaemia were similar (30 (5-164) pg/ml and 29 (9-152), p = 0.79). Adrenaline concentrations at biochemical hypoglycaemia increased from normoglycaemia at diabetes duration < 16 years (p = 0.03). In first trimester, adrenaline concentrations were comparable in women with or without severe hypoglycaemia (24 (14-164) pg/ml vs. 33 (5-86), p = 0.35). Noradrenaline, glucagon and cortisol concentrations did not increase during biochemical hypoglycaemia.

CONCLUSION

Adrenaline response to biochemical hypoglycaemia was present at similar levels in early and late pregnancy, particularly in shorter diabetes duration, and was not associated with severe hypoglycaemia in early pregnancy.

Hypoglycaemia during pregnancy in women with Type 1 diabetes

AIMS

To explore incidence, risk factors, possible pathophysiological factors and clinical management of hypoglycaemia during pregnancy in women with Type 1 diabetes.

METHODS

Literature review.

RESULTS

In women with Type 1 diabetes, severe hypoglycaemia occurs three to five times more frequently in early pregnancy than in the period prior to pregnancy, whereas in the third trimester the incidence of severe hypoglycaemia is lower than in the year preceding pregnancy. The frequency distribution of severe hypoglycaemia is much skewed, as 10% of the pregnant women account for 60% of all recorded events. Risk factors for severe hypoglycaemia during pregnancy include a history with severe hypoglycaemia in the year preceding pregnancy, impaired hypoglycaemia awareness, long duration of diabetes, low HbA(1c) in early pregnancy, fluctuating plasma glucose values (≤ 3.9 mmol/l or ≥ 10.0 mmol/l) and excessive use of supplementary insulin injections between meals. Pregnancy-induced nausea and vomiting seem not to be contributing factors.

CONCLUSIONS

Striving for near-normoglycaemia with focus on reduction of plasma glucose fluctuations during pregnancy should have high priority among clinicians with the persistent aim of improving pregnancy outcome among women with Type 1 diabetes. Pre-conception counselling, carbohydrate counting, use of insulin analogues, continuous subcutaneous insulin infusion (insulin pump) therapy and real-time continuous glucose monitoring with alarms for low glucose values might be relevant tools to obtain near-normoglycaemia without episodes of severe hypoglycaemia.

Lower levels of circulating IGF-I in Type 1 diabetic women with frequent severe hypoglycaemia during pregnancy

AIMS

Severe hypoglycaemia is a significant problem in pregnant women with Type 1 diabetes. We explored whether frequent severe hypoglycaemia during pregnancy in women with Type 1 diabetes is related to placental growth hormone (GH) and insulin-like growth factor I (IGF-I) levels.

METHODS

A prospective, observational study of 107 consecutive pregnant women with Type 1 diabetes. Blood samples were drawn for IGF-I and placental GH analyses at 8, 14, 21, 27 and 33 weeks. Severe hypoglycaemic events were reported within 24 h.

RESULTS

Eleven women (10%) experienced frequent severe hypoglycaemia (> or = 5 events), accounting for 60% of all events. Throughout pregnancy, IGF-I levels were 25% lower in these women (P < 0.005) compared with the remaining women, despite similar placental GH levels. Eighty per cent of the severe hypoglycaemic events occurred before 20 weeks when IGF-I levels were at their lowest. This finding was not explained by differences in insulin dose, median plasma glucose levels or glycated haemoglobin. History of severe hypoglycaemia the year preceding pregnancy and impaired hypoglycaemia awareness-being the only predictors of frequent severe hypoglycaemia in a logistic regression analysis-were not associated with IGF-I or placental GH levels at 8 weeks.

CONCLUSIONS

In women with Type 1 diabetes experiencing frequent severe hypoglycaemia during pregnancy, IGF-I levels are significantly lower compared with the remaining women despite similar placental GH levels. IGF-I levels are lowest in early pregnancy where the incidence of severe hypoglycaemia is highest. IGF-I may be a novel factor of interest in the investigation of severe hypoglycaemia in patients with Type 1 diabetes.

Twin-pregnancy increases susceptibility of ewes to hypoglycaemic stress and pregnancy toxaemia

Pregnancy toxaemia is a metabolic disorder with a high mortality rate and occurs in twin-bearing ewes in late gestation. Maternal hypoglycaemia is a characteristic symptom of the disease and has been attributed to an increase in glucose uptake by the twin-bearing uterus. The possibility that a reduced maternal glucose production rate might cause hypoglycaemia, has received little attention in the past. It was the aim of this study to investigate this explanation as a possible alternative. Six ewes were sequentially subjected to two types of hypoglycaemic stress, firstly by fasting for 14 h and secondly through induction of moderate hyperketonaemia. Glucose kinetics were assessed in each animal during the dry non-gestational period, during late gestation, and during early lactation. Application of these stress factors was associated with variation of plasma glucose concentration from 4.9 to 0.87 mmol L(-1). The plasma glucose concentration was always significantly related to the glucose production rate. The greatest stress-induced reductions in glucose concentration and glucose production rate were seen during late gestation in twin-bearing ewes. The decline in the glucose production rate after an overnight fast and during induced hyperketonaemia was greater in twin-bearing ewes than in single-bearing ewes (59% and 43%, respectively, p<0.05). The stress conditions resulted in the lowest levels of glucose concentration and glucose turnover rates in the stressed, hyperketonaemic, late gestation twin-bearing ewes. This illustrates that the glucose homoeostatic system of ewes bearing twins is significantly more susceptible to hypoglycaemic stress than that of ewes bearing single lambs. These findings also show that the primary cause of hypoglycaemia in late gestation twin-pregnant ewes is an increased susceptibility to a stress related reduction in glucose production rate. This metabolic condition leaves the twin-pregnant ewe predisposed for the development of pregnancy toxaemia.

Glucagon secretion and autonomic signaling during hypoglycemia in late pregnancy

We examined net pancreatic norepinephrine (NE) spillover, pancreatic polypeptide (PP) release, and the decrement in C-peptide to identify factors involved in the blunted counterregulatory glucagon response in pregnancy. Conscious pregnant [pregnant hypoglycemic (Ph); 3rd trimester; n = 8] and nonpregnant [nonpregnant hypoglycemic (NPh); n = 6] dogs were studied during insulin-induced (approximately 12-fold basal insulin concentrations) hypoglycemia (plasma glucose 3.1 mM). Additional dogs were studied during hyperinsulinemic euglycemia [nonpregnant euglycemic (NPe), n = 4; pregnant euglycemic (Pe), n = 5; plasma glucose 6 mM]. Arterial glucagon concentrations declined similarly in NPe and Pe. Areas under the curve (AUCs) of the changes in glucagon and epinephrine were seven- and threefold greater in NPh than Ph (P < 0.05 between groups for both). Glucagon secretion fell below basal in NPe, Pe, and Ph but rose significantly in NPh. C-peptide declined 0.25 +/- 0.06, 0.12 +/- 0.11, 0.28 +/- 0.05, and 0.13 +/- 0.02 ng/ml in NPe, Pe, NPh, and Ph, respectively (P < 0.05, NPh vs. Ph). AUCs of NE spillover were 516 +/- 274, 265 +/- 303, 506 +/- 94, and -63 +/- 79 ng, respectively (P < 0.05, NPh vs. Ph). The AUC of PP release was approximately threefold greater in NPh than Ph (P < 0.05) but not different between euglycemic groups. The current evidence strongly suggests that the blunting of glucagon secretion during insulin-induced hypoglycemia in pregnancy is related to generalized impairment of a number of different signals, including parasympathetic and sympathoadrenal stimuli and altered sensing of circulating and/or intraislet insulin.

Chronic estradiol and progesterone treatment in conscious dogs: effects on insulin sensitivity and response to hypoglycemia

We evaluated the effect of chronic (3 wk) subcutaneous treatment with progesterone and estradiol (PE; producing serum levels observed in the 3rd trimester of pregnancy) or placebo (C) on hepatic and whole body insulin sensitivity and response to hypoglycemia in conscious, overnight-fasted nonpregnant female dogs, using tracer and arteriovenous difference techniques. Insulin was infused peripherally for 3 h at 1.8 mU x kg(-1) x min(-1). Glucose was allowed to fall to 3 mM (Hypo) or maintained at 6 mM (Eugly) by peripheral glucose infusion. Insulin concentrations were significantly higher in Eugly-PE (n = 7) and Hypo-PE (n = 7) than in Eugly-C (n = 6) and Hypo-C groups (n = 7), but there were no significant differences in hepatic insulin extraction. Concentrations of glucagon, cortisol, epinephrine, and norepinephrine did not differ significantly between Eugly groups or between Hypo groups. Whole body glucose disposal, adjusted for the differences in insulin between groups, was 35% higher in Eugly-C vs. Eugly-PE groups (P < 0.05). Eugly-C and Eugly-PE groups exhibited similar rates of net hepatic glucose uptake, but the rate of glucose appearance was greater in Eugly-PE in the last hour (P < 0.05). Net hepatic glucose output was greater (P < 0.05) in Hypo-PE than in Hypo-C groups, and the glucose infusion rate required to maintain equivalent hypoglycemia was less (P < 0.05). The rate of gluconeogenic flux did not differ between Hypo groups. Chronic progesterone and estradiol exposure caused whole body (primarily skeletal muscle) insulin resistance and enhanced the liver's response to hypoglycemia without altering counterregulatory hormone concentrations.

Optimizing insulin therapy in pregnant women with type 1 diabetes mellitus

Pregnancy complicated by type 1 diabetes mellitus is associated with an increased risk of complications in the mother and infant. Normal or near normal glycemic control prior to and during pregnancy reduces many of these risks to levels observed in the general population. This degree of glycemic control is generally achievable only with intensive insulin therapy: multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII) via an insulin pump. These therapeutic regimens have been found to result in comparable glycemic control, although CSII provides increased flexibility in terms of patient lifestyle, and may reduce the incidence of hypoglycemia. Frequent home blood glucose monitoring is imperative during pregnancy in order to optimize glycemic control and reduce the risk of hypoglycemia. Furthermore, insulin requirements change significantly over the course of pregnancy. The new short-acting insulin analogs, insulin lispro and insulin aspart, have pharmacodynamic properties which make them ideal for use during pregnancy. Although the number of published studies evaluating the use of insulin lispro during pregnancy is limited, the majority support its safety. No studies of insulin aspart in pregnancy have been published in full. In addition to optimization of glycemic control, frequent assessment for development and/or progression of microvascular complications is necessary during pregnancy.

Pregnancy impairs the counterregulatory response to insulin-induced hypoglycemia in the dog

The impact of pregnancy on the counterregulatory response to insulin-induced hypoglycemia was examined in six nonpregnant (NP) and six pregnant (P; 3rd trimester) conscious dogs by tracer and arteriovenous difference techniques. After basal sampling, insulin was infused intraportally at 30 pmol.kg(-1).min(-1) for 180 min. Insulin rose from 70 +/- 15 to 1,586 +/- 221 pmol/l and 27 +/- 4 to 1,247 +/- 61 pmol/l in the 3rd h in NP and P, respectively. Arterial glucose fell from 5.9 +/- 0.2 to 2.3 +/- 0.2 mmol/l in P. Glucose was infused in NP to equate the rate of fall of glucose and the steady-state concentrations in the groups (5.9 +/- 0.2 to 2.3 +/- 0.1 mmol/l in NP). Glucagon was 32 +/- 6, 69 +/- 11, and 48 +/- 10 ng/l (basal and 1st and 3rd h) in NP, but the response was attenuated in P (34 +/- 5, 46 +/- 6, 41 +/- 9 ng/l). Cortisol and epinephrine rose similarly in both groups, but norepinephrine rose more in NP (Delta3.01 +/- 0.46 and Delta1.31 +/- 0.13 nmol/l, P < 0.05). Net hepatic glucose output (NHGO; micromol.kg(-1).min(-1)) increased from 10.6 +/- 1.8 to 21.2 +/- 3.3 in NP (3rd h) but did not increase in P (15.1 +/- 1.5 to 15.3 +/- 2.8 micromol.kg(-1).min(-1), P < 0.05 between groups). The glycogenolytic contribution to NHGO in NP increased from 5.8 +/- 0.7 to 10.4 +/- 2.5 micromol.kg(-1).min(-1) by 90 min but steadily declined in P. The increase in glycerol levels and the gluconeogenic contribution to NHGO were 50% less in P than in NP, but ketogenesis did not differ. The glucagon and norepinephrine responses to insulin-induced hypoglycemia are blunted in late pregnancy in the dog, impacting on the magnitude of the metabolic responses to the fall in glucose.

Maternal hypoglycemia during pregnancy in type 1 diabetes: maternal and fetal consequences

There is strong evidence that the avoidance of hyperglycemia is essential inoptimizing pregnancy outcome in type 1 diabetes. The price to pay is a striking increase in severe hypoglycemia (SH), defined as episodes requiring help from another person. During type 1 diabetic pregnancy, occurrence rates of SH up to 15 times higher as in the intensively treated group of the Diabetes Control and Complications Trial (DCCT) are reported. Blood glucose (BG) treatment targets differ considerably between clinics; some authors advocate lower limits as low as 3.3 mmol/l. Improved glycemic control and/or recurrent hypoglycemia (i.e. BG <3.9 mmol/l) may result in impairment of glucose counterregulatory responses. Also, glucose counterregulation may be altered by pregnancy itself. Short-acting insulin analogs may help reduce hypoglycemia with preservation of good glycemic control, but their use during pregnancy has yet to be proven safe.Several clinical studies did not establish an association between maternal hypoglycemia and diabetic embryopathy. However, animal studies clearly indicate that hypoglycemia is potentially teratogenic during organogenesis. Increased rates of macrosomia continue to be observed despite near normal HbA(1c) levels. This may, at least in part, be the result of rebound hyperglycemia elicited by hypoglycemia. Exposure to hypoglycemia in utero may have long-term effects on offspring including neuropsychological defects. It is yet unclear to what extent the benefits of tight glycemic control balance with the increased risk of (severe) hypoglycemia during type 1 diabetic pregnancy. Efforts must be made to avoid low BG, i.e. <3.9 mmol/l, when tightening glycemic control.

Medical complications of diabetes mellitus in pregnancy

Many women with diabetes develop complications of their chronic disease that may have a tremendous impact on their quality of life and their ultimate prognosis. Because Type 1 diabetes often begins at a very early age, it is quite common for women in their child-bearing years to be affected by these complications. As described in this article, diabetic complications and pregnancy may significantly affect each other, but it is not always easy to predict the course of either and to counsel these patients accordingly. Nevertheless, it appears that only in rare occasions should women with diabetes be advised against pregnancy, and that in most situations, with careful and knowledgeable management, a favorable outcome of pregnancy can be expected both for the mother and her infant.

Glycemic control in the diabetic pregnancy: is tighter always better?

Glucose is the principal nutrient that the mother supplies to the fetus through the placenta by way of concentration-dependent mechanisms. In the presence of maternal hypoglycemia, with limited glucose supply, fetal hypoglycemia and hypoinsulinism ensue. This may be viewed as an adaptive mechanism to increase the chances of fetal survival in the face of limited maternal supply, albeit of a growth-restricted fetus. Fetal nutrient deprivation and the resulting hypoinsulinism may have both short- and long-term consequences. Intrauterine growth failure is associated with higher rates of gestational age-specific neonatal mortality and with long-term cognitive deficits. Furthermore, epidemiologic data suggest that diabetes, coronary artery disease, and hypertension are more common among adults who were small for gestational age at birth. Thus, pancreatic failure in adulthood may be either a response to excessive exposure to glucose as a result of maternal hyperglycemia, or as a result of hypoglycemia where nutrient deprivation leads to fetal growth restriction and reduced islet cell proliferation. Because low mean concentrations of maternal glucose in gestational diabetes are associated with an increased risk of fetal growth restriction, overzealous glycemic control during pregnancy may raise concerns regarding the possible effects on the infant. In the mother with Type 1 diabetes, strict glycemic control is often associated with an increased incidence of severe hypoglycemia. Up to 40% of women report at least one episode of severe hypoglycemia during pregnancy, requiring assistance by another person or professional intervention. It is quite possible that in some patients striving to optimize pregnancy outcome by maintaining the best possible glycemic control jeopardizes the well-being of the mother and the fetus. Thus, with respect to tight glycemic control of pregnant women with diabetes, the question arises: How tight is too tight? Is there a threshold below which the trade-off in terms of maternal morbidity as well as fetal growth restriction and its consequences outweighs the benefits of preventing the effects of maternal hyperglycemia?

Fetal heart-rate monitoring during maternal hypoglycaemic coma: a case report

Contradictory descriptions exist concerning the fetal heart-rate (FHR) patterns that appear during maternal hypoglycaemia. We report a case of maternal hypoglycaemic coma during which a FHR tracing was obtained showing a normal type D accelerative pattern.

Placental hormones during induced hypoglycaemia in pregnant women with insulin-dependent diabetes mellitus: evidence of an active role for placenta in hormonal counter-regulation

OBJECTIVE

To study the effect of induced hypoglycaemia on serum levels of the placental hormones oestriol, human placental lactogen, placental growth hormone and progesterone in the third trimester of pregnancy.

DESIGN

A prospective experimental investigation.

SETTING

High risk pregnancy unit and diabetes research unit at Karolinska Institutet Danderyd Hospital, a university hospital.

PARTICIPANTS

Ten women with insulin-dependent diabetes mellitus in the third trimester of pregnancy.

METHODS

Venous blood samples were collected every 15 minutes for analyses of oestriol, progesterone, human placental lactogen and placental growth hormone, during the 150 min of a hyperinsulinaemic hypoglycaemic clamp, which maintained arterial blood-glucose level of about 2.2 mmol/l.

MAIN OUTCOME MEASURES

Levels of analysed placental hormones during hypoglycaemia.

RESULTS

A statistically significant increase was observed in placental growth hormone during hypoglycaemia (P < 0.0001), whereas the placental hormones progesterone, human placental lactogen and oestriol did not show changes of clinical significance.

CONCLUSIONS

The increase in placental growth hormone indicates that the placenta is an endocrine organ which may take an active part in acute metabolic processes, such as here in the hormonal counterregulation of hypoglycaemia.

Mouse embryonic cardiac metabolism under euglycemic and hypoglycemic conditions

Children of mothers with insulin-dependent diabetic mothers (IDDM) have a 2-4 times higher incidence of congenital birth defects as compared to the general population, including cardiac abnormalities, of unknown etiology. Using rodent embryos to explore potential teratogenic factors of the altered IDDM metabolism, it has been shown that exposure to hypoglycemia in vitro results in a variety of defects, including cardiac malformations. Since pregnant diabetics experience frequent episodes of low blood glucose, it was hypothesized that hypoglycemia may play a role in the generation of heart abnormalities seen in children born to IDDM mothers. Several studies have indicated that during embryogenesis the heart is dependent on glucose for energy production such that under hypoglycemic conditions, insufficient amounts of ATP may be produced resulting in abnormalities. To test this hypothesis, cardiac ATP content was monitored in D10-D12 (plug day = D1) hearts. In addition, the contribution of glycolysis and the Krebs cycle to ATP production was monitored. D10 hearts exposed to euglycemic control conditions were found to be primarily dependent on glycolysis for ATP production from glucose before switching to the Krebs cycle and oxidative phosphorylation for energy production from this substrate on D11. Exposure to hypoglycemia did not alter the timing of this maturation process or deplete cardiac ATP content. However, cardiac lactate levels increased approximately twofold in the presence of hypoglycemia on d10. Since increased concentrations of lactate are harmful to many tissues and have been shown to be detrimental to the adult rat heart, lactic acidosis may explain the origin of cardiac defects produced by hypoglycemia, and not a deficiency of ATP.

Effects of hypoglycaemia on fetal heart activity and umbilical artery Doppler velocity waveforms in pregnant women with insulin-dependent diabetes mellitus

OBJECTIVE

To study the effect of induced hypoglycaemia on fetal wellbeing as indicated by fetal heart rate and umbilical artery flow velocity waveforms.

DESIGN

A prospective experimental investigation.

SETTING

High risk pregnancy unit and diabetes research unit at Karolinska Institutet, Danderyd Hospital, a university affiliated hospital.

PARTICIPANTS

Ten women with insulin-dependent diabetes mellitus in the third trimester of pregnancy.

INTERVENTIONS

The fetal heart rate, the blood flow velocity waveforms in the umbilical artery and the maternal catecholamine levels were investigated during a 150-minute hyperinsulinaemic hypoglycaemic clamp with induction and maintenance of an arterial blood glucose level of about 2.2 mmol/l.

MAIN OUTCOME MEASURES

1. Fetal: changes of fetal heart rate pattern and pulsatility index of the umbilical artery flow velocity waveforms. 2. Maternal: levels of plasma adrenaline and plasma noradrenaline.

RESULTS

Maternal hypoglycaemia was associated with an increase in frequency and amplitude of fetal heart rate accelerations, a slight decrease in the pulsatility index of the umbilical artery and a rise in the maternal catecholamine levels.

CONCLUSIONS

We speculate that the increased number of fetal heart rate accelerations reflects an increased sympathico-adrenal activity during the hypoglycaemia clamp. No potentially harmful effects on the fetus were observed in the fetal heart rate or in the umbilical artery Doppler waveform analysis during hypoglycaemia.

Management of hypoglycemia and diabetic ketoacidosis in pregnancy

The article discusses the incidence and management of hypoglycemia and diabetic ketoacidosis (DKA) in pregnancy. Additional topics addressed are the incidence of hypoglycemia, pathophysiology, diagnosis and management of hypoglycemia in pregnancy, fetal monitoring with short- and long-term fetal sequelae, and prevention of hypoglycemic recurrences. Subsequently, attention is focused on the diagnosis and management of hyperglycemia and DKA in pregnancy.

Fetal Doppler and behavioral responses during hypoglycemia induced with the insulin clamp technique in pregnant diabetic women

OBJECTIVE

This study was undertaken to assess human fetal behavior and fetal blood flow after insulin-induced symptomatic maternal hypoglycemia of sufficient magnitude to elicit counterregulatory hormones and a symptomatic response.

STUDY DESIGN

Plasma glucose was lowered from approximately 95 mg/dl to 45 mg/dl in decrements of 10 mg/dl every 40 minutes with the insulin clamp technique. In 10 insulin-dependent diabetic women in the third trimester, the fetus was studied by monitoring fetal heart rate and recording fetal body and breathing movements and by performing Doppler waveform analysis with real-time ultrasonography. Maternal levels of glucagon, cortisol, epinephrine, and growth hormone were measured at each plasma glucose level.

RESULTS

The mean number of fetal limb and body movements at the start of the study was 25 +/- 16 per 15 minutes, which increased to a mean of 38 +/- 28 at a glucose level of 60 mg/dl and then declined to a mean of 23 +/- 10 at a glucose level of approximately 45 mg/dl. These changes, however, did not achieve statistical significance. In addition, no significant reductions in fetal breathing movements or heart rate were observed, although maternal epinephrine and growth hormone levels were significantly (p < 0.001) increased. No consistent changes in Doppler velocity waveforms were observed.

CONCLUSION

These data suggest that fetal well-being remains unaltered in spite of moderate maternal hypoglycemia in diabetic women.

Normalization of blood glucose in insulin-dependent diabetic pregnancies and the risks of hypoglycemia: a therapeutic dilemma

Intensive insulin therapy delays the onset and progression of microvascular complications in insulin-dependent diabetes mellitus (IDDM). Such therapy, however, is associated with an increased risk of potentially life-threatening hypoglycemia due to the loss of normal counterregulatory hormonal responses to hypoglycemia and to the syndrome of hypoglycemia unawareness. Current standards for glycemic control during pregnancy in IDDM women require intensive insulin therapy to optimize pregnancy outcome. Therefore, obstetricians and gynecologists providing prenatal care for women with IDDM should be aware that intensive insulin therapy predisposes these patients to the significant risks of severe hypoglycemia. It often becomes necessary to individualize the optimal balance between glycemic control during pregnancy and the risks of hypoglycemia.

Metabolic interactions of diabetes and pregnancy

Many of the embryonic and fetal abnormalities that occur in pregnancies complicated by maternal diabetes are the result of development in a metabolically abnormal environment. Diabetic embryopathy (birth defects and spontaneous abortions) results from maternal metabolic abnormalities during the first 6-7 weeks of gestation. The embryopathy appears to be multifactorial in origin, and the resulting defects remain important causes of morbidity and mortality in diabetic pregnancies. Diabetic fetopathy (predominantly macrosomia and neonatal hypoglycemia) results from fetal overnutrition and hyperinsulinemia during the second and third trimesters. Fetopathy may cause significant morbidity not only in the perinatal period, but also in later life as overweight infants grow up to be overweight children and young adults. Careful regulation of maternal metabolism from the preconceptional period onward can reduce greatly or even eliminate the excess risks that have been incurred by infants of diabetic mothers in the past. Successful management of maternal diabetes requires knowledge of the alterations in intermediary metabolism that normally occur during pregnancy, as discussed in this chapter.

Gender influences counterregulatory hormone responses to hypoglycemia

It has been generally assumed that counterregulatory hormone responses to hypoglycemia are not influenced by gender. To test this assumption, we analyzed three separate hypoglycemic insulin clamp studies in age-matched, healthy, non-obese females (n = 33) and males (n = 37). In one study (12 females, 17 males), plasma glucose level was rapidly decreased to about 57 mg/dL for 100 minutes with a 0.65-mU/kg/min insulin infusion. Despite an identical decrease in glucose level, the increase in epinephrine (361 +/- 64 v 188 +/- 38 pg/mL, P < .05), norepinephrine (132 +/- 28 v 47 +/- 19 pg/mL, P < .01), and growth hormone ([GH] 16.0 +/- 3.8 v 4.9 +/- 1.9 ng/mL, P < .05) levels, but not glucagon or cortisol levels, were significantly greater in males than in females, respectively. In the second study (10 females, eight males), a 5.0-mU/kg/min insulin infusion was used to decrease glucose levels to 55 mg/dL for 180 minutes. Epinephrine (P < .05) and GH (P < .01) responses were greater in males than in females. In a third study (11 females, 12 males), plasma glucose level was gradually decreased to about 50 mg/dL over 240 minutes. Again epinephrine (P < .01), norepinephrine (P < .01), GH (P < .05), and cortisol (P < .01) responses were nearly twofold greater in males (P < .01). Multivariate analysis of all 70 subjects identified gender as the most significant factor contributing to the epinephrine (P < .001) and norepinephrine (P < .005) responses, and also as a significant contributor to the GH response (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypoglycaemia in pregnancy

Normally there is a very close relationship between maternal and fetal glucose concentrations during both early and late gestation. Maternal hypoglycaemia during pregnancy will therefore not only affect the mother herself but also the conceptus. As can be judged from the literature, acute hypoglycaemic episodes are only rarely seen in non-diabetic pregnancies. In recent years it has become increasingly evident that insulin-dependent diabetic patients, whether pregnant or not, run a much increased risk of having severe hypoglycaemia (SH) attacks (i.e. the patient needs the assistance of another person to relieve the attack) whenever attempts are made to introduce tight blood glucose control. Very high incidence rates of SH between 19% and 44% have been reported in diabetic pregnancy. Episodes of SH could have serious consequences; neuroglycopenia seems especially hazardous for the mother particularly during the performance of a critical task like driving a car. While hypoglycaemia has embryopathic effects in rodents, there are no data in the human to support a teratogenic effect. Insulin-induced hypoglycaemia in the last trimester of diabetic pregnancy may increase fetal body movement and decrease the fetal heart rate variability. A number of very rare conditions such as insulinoma, severe malaria, HELLP syndrome (haemolysis, elevated liver enzymes, low platelet count), severe fulminating liver disease, and ACTH and/or growth hormone deficiency have been reported to be associated with SH. Relative hypoglycaemia--i.e. low fasting blood glucose and 'flat' glucose tolerance test--is frequently seen in normotensive pregnant women with intrauterine fetal growth retardation. This pattern of maternal carbohydrate metabolism could lead to fetal hypoglycaemia and hypoinsulinaemia and contribute to poor fetal growth.