Peter H. Bisschop

Significance of (sub)clinical thyroid dysfunction and thyroid autoimmunity before conception and in early pregnancy: a systematic review

BACKGROUND Thyroid dysfunction and thyroid autoimmunity are prevalent among women of reproductive age and are associated with adverse pregnancy outcomes. Preconception or early pregnancy screening for thyroid dysfunction has been proposed but is not widely accepted. We conducted a systematic review of the literature on the clinical significance of thyroid dysfunction and thyroid autoimmunity before conception and in early pregnancy. METHODS Relevant studies were identified by searching Medline, EMBASE and the Cochrane Controlled Trials Register. RESULTS From a total of 14 208 primary selected titles, 43 articles were included for the systematic review and 38 were appropriate for meta-analyses. No articles about hyperthyroidism were selected. Subclinical hypothyroidism in early pregnancy, compared with normal thyroid function, was associated with the occurrence of pre-eclampsia [odds ratio (OR) 1.7, 95% confidence interval (CI) 1.1-2.6] and an increased risk of perinatal mortality (OR 2.7, 95% CI 1.6-4.7). In the meta-analyses, the presence of thyroid antibodies was associated with an increased risk of unexplained subfertility (OR 1.5, 95% CI 1.1-2.0), miscarriage (OR 3.73, 95% CI 1.8-7.6), recurrent miscarriage (OR 2.3, 95% CI 1.5-3.5), preterm birth (OR 1.9, 95% CI 1.1-3.5) and maternal post-partum thyroiditis (OR 11.5, 95% CI 5.6-24) when compared with the absence of thyroid antibodies. CONCLUSIONS Pregnant women with subclinical hypothyroidism or thyroid antibodies have an increased risk of complications, especially pre-eclampsia, perinatal mortality and (recurrent) miscarriage. Future research, within the setting of clinical trials, should focus on the potential health gain of identification, and effect of treatment, of thyroid disease on pregnancy outcome.

Estradiol Regulates Brown Adipose Tissue Thermogenesis via Hypothalamic AMPK

Summary Estrogens play a major role in the modulation of energy balance through central and peripheral actions. Here, we demonstrate that central action of estradiol (E2) inhibits AMP-activated protein kinase (AMPK) through estrogen receptor alpha (ERα) selectively in the ventromedial nucleus of the hypothalamus (VMH), leading to activation of thermogenesis in brown adipose tissue (BAT) through the sympathetic nervous system (SNS) in a feeding-independent manner. Genetic activation of AMPK in the VMH prevented E2-induced increase in BAT-mediated thermogenesis and weight loss. Notably, fluctuations in E2 levels during estrous cycle also modulate this integrated physiological network. Together, these findings demonstrate that E2 regulation of the VMH AMPK-SNS-BAT axis is an important determinant of energy balance and suggest that dysregulation in this axis may account for the common changes in energy homeostasis and obesity linked to dysfunction of the female gonadal axis.

Lipodystrophy in Hiv-1-positive patients is associated with insulin resistance in multiple metabolic pathways

BackgroundTreatment for HIV-1 infection is complicated by fat redistribution (lipodystrophy). This is associated with insulin resistance concerning glucose uptake. Our aim was to characterize glucose metabolism more comprehensively in HIV-1-infected patients with lipodystrophy. We assessed glucose disposal and its pathways, glucose production, plasma free fatty acid (FFA) levels, and the degree to which these parameters could be suppressed by insulin. MethodsSix HIV-1-infected men on protease inhibitor-based HAART with lipodystrophy (HIV+LD) were studied. The results were compared with those in six matched healthy male volunteers. Insulin sensitivity was quantified by hyperinsulinemic euglycaemic clamp. Glucose production and uptake were assessed by tracer dilution employing 6,6d2-glucose. ResultsAt post-absorptive insulin concentrations, glucose production was 47% higher in HIV+LD than controls (P = 0.025). During clamp, glucose production was suppressed by 53% in HIV+LD, but by 85% in controls (P = 0.004). Glucose disposal increased in both groups, but by only 27% in HIV+LD versus 201% in controls (P = 0.004). Consequently, insulin-stimulated total glucose disposal was lower in HIV+LD patients (P = 0.006). Non-oxidative glucose disposal as percentage of total disposal did not differ significantly between groups (63% in HIV+LD and 62% in controls). Baseline plasma FFA concentrations were higher (0.60 versus 0.35 mmol/l;P = 0.024), whereas FFA decline during hyperinsulinemia was less (65 versus 85%;P = 0.01) in HIV+LD versus controls . ConclusionsPost-absorptive glucose production is increased in HIV-1-infected patients with lipodystrophy. Moreover, both the ability of insulin to suppress endogenous glucose production and lipolysis, and to stimulate peripheral glucose uptake and its metabolic pathways is reduced, indicating severe resistance concerning multiple effects of insulin.

Thyroid hormone modulates glucose production via a sympathetic pathway from the hypothalamic paraventricular nucleus to the liver

Thyrotoxicosis increases endogenous glucose production (EGP) and induces hepatic insulin resistance. We have recently shown that these alterations can be modulated by selective hepatic sympathetic and parasympathetic denervation, pointing to neurally mediated effects of thyroid hormone on glucose metabolism. Here, we investigated the effects of central triiodothyronine (T3) administration on EGP. We used stable isotope dilution to measure EGP before and after i.c.v. bolus infusion of T3 or vehicle in euthyroid rats. To study the role of hypothalamic preautonomic neurons, bilateral T3 microdialysis in the paraventricular nucleus (PVN) was performed for 2 h. Finally, we combined T3 microdialysis in the PVN with selective hepatic sympathetic denervation to delineate the involvement of the sympathetic nervous system in the observed metabolic alterations. T3 microdialysis in the PVN increased EGP by 11 ± 4% (P = 0.020), while EGP decreased by 5 ± 8% (ns) in vehicle-treated rats (T3 vs. Veh, P = 0.030). Plasma glucose increased by 29 ± 5% (P = 0.0001) after T3 microdialysis versus 8 ± 3% in vehicle-treated rats (T3 vs. Veh, P = 0.003). Similar effects were observed after i.c.v. T3 administration. Effects of PVN T3 microdialysis were independent of plasma T3, insulin, glucagon, and corticosterone. However, selective hepatic sympathectomy completely prevented the effect of T3 microdialysis on EGP. We conclude that stimulation of T3-sensitive neurons in the PVN of euthyroid rats increases EGP via sympathetic projections to the liver, independently of circulating glucoregulatory hormones. This represents a unique central pathway for modulation of hepatic glucose metabolism by thyroid hormone.

Treatment of thyroid disorders before conception and in early pregnancy: a systematic review

BACKGROUND Thyroid disorders are associated with pregnancy complications. Universal screening is currently not recommended because of a lack of evidence on the effectiveness of treatment. Women with hyperthyroidism and hypothyroidism evidently require treatment but this is less clear for women with subclinical hypothyroidism and thyroid autoimmunity. Therefore, we conducted a systematic review to provide a comprehensive overview on the available treatment interventions. METHODS Relevant studies were identified by searching Medline, EMBASE and Cochrane Controlled Trials Register, published until December 2011. RESULTS From a total of 7334 primary selected titles, 22 articles were included for the systematic review and 11 were appropriate for meta-analyses. Eight studies reported on hyperthyroidism. Propylthiouracil (PTU) and methimazole reduce the risk for preterm delivery [risk ratio (RR): 0.23, confidence interval (CI): 0.1-0.52], pre-eclampsia (RR: 0.23, CI: 0.06-0.89) and low birthweight (RR: 0.38, CI: 0.22-0.66). The nine studies that reported on clinical hypothyroidism showed that levothyroxine is effective in reducing the risk for miscarriage (RR: 0.19, CI: 0.08-0.39) and preterm delivery (RR: 0.41, CI: 0.24-0.68). For treatment of subclinical hypothyroidism, current evidence is insufficient. The five studies available on thyroid autoimmunity showed a not significant reduction in miscarriage (RR: 0.58, CI: 0.32-1.06), but significant reduction in preterm birth by treatment with levothyoxine (RR: 0.31, CI: 0.11-0.90). CONCLUSION For hyperthyroidism, methimazole and PTU are effective in preventing pregnancy complications. For clinical hypothyroidism, treatment with levothyroxine is recommended. For subclinical hypothyroidism and thyroid autoimmunity, evidence is insufficient to recommend treatment with levothyroxine. The overall lack of evidence precludes a recommendation for universal screening and is only justified in a research setting.

Cortisol, interleukins and S100B in delirium in the elderly.

In independent studies delirium was associated with higher levels of cortisol, interleukin(IL)s, and S100B. The aim of this study was to simultaneously compare cortisol, IL-6, IL-8, and S100B levels in patients aged 65years and older admitted for hip fracture surgery with and without delirium. Cortisol, IL-6, IL-8, and S100B were assayed in repeated blood samples. 120 patients (mean age 84years, 62 patients with delirium) were included. Highest levels of IL-8 (27.1, 95% Confidence Interval (CI): 13.6-53.1pg/ml) and cortisol (666, 95% CI: 475-859nmol/L) were before delirium, but of IL-6 (84.3, 95% CI: 46.5-151.4pg/mL) and S100B (0.18, 95% CI: 0.12-0.24 microg/L) during delirium. In multivariable analysis cortisol, LogIL-6, and LogS100B were significantly associated with delirium, but adjusted for pre-existing cognitive impairment, only LogS100B remained significantly associated. Cortisol, IL-6 and S100B may have a role in the pathogenesis of delirium, but S100B is the strongest independent marker.

Low accuracy of tumor markers for diagnosing pancreatic neuroendocrine tumors in multiple endocrine neoplasia type 1 patients

CONTEXT The assessment of tumor markers for diagnosing pancreatic neuroendocrine tumors (pNET) in multiple endocrine neoplasia type 1 (MEN1) patients is advised in the current guidelines but has never been validated for this purpose. OBJECTIVE The objective of the study was to assess the diagnostic accuracy of chromogranin A (CgA), pancreatic polypeptide (PP), and glucagon for pNET in MEN1. DESIGN This was a diagnostic study. SETTING The study was conducted at Dutch university medical centers from 2008 to 2011, representing 90% of the total Dutch MEN1 population. PATIENTS AND METHODS Patients for whom data on tumor markers in combination with the reference standard (ie, radiological imaging) were available between 2008 and 2011 were included. The reference standard for the presence of pNET was pathology or detection on magnetic resonance imaging, computed tomography, or endoscopic ultrasound confirmed on subsequent imaging, irrespective of modality at follow-up. MAIN OUTCOME MEASURES The area under the receiver-operating characteristic curve (AUC), positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio, sensitivity, and specificity were calculated for each marker. RESULTS For the analysis of PP, CgA, and glucagon, 73, 81, and 94 patients were available, respectively. The AUC for CgA was 0.48 [95% confidence interval (CI) 0.35-0.61] with a sensitivity 0.33 and a specificity 0.73; the AUC for glucagon was 0.58 (95% CI 0.46-0.70) with a sensitivity 0.43 and a specificity 0.73; and the AUC for PP was 0.64 (95% CI 0.50-0.77) with a sensitivity 0.36 and a specificity 0.74. Age, imaging modality, tumor size, and number did not influence the outcomes. CONCLUSION The diagnostic accuracy of the tumor markers CgA, PP, and glucagon for pNET in MEN1 is low.

Low prevalence of hypopituitarism after traumatic brain injury: a multicenter study

OBJECTIVE Hypopituitarism after traumatic brain injury (TBI) is considered to be a prevalent condition. However, prevalence rates differ considerably among reported studies, due to differences in definitions, endocrine assessments of hypopituitarism, and confounding factors, such as timing of evaluation and the severity of the trauma. Aim To evaluate the prevalence of hypopituitarism in a large cohort of TBI patients after long-term follow-up using a standardized endocrine evaluation. Study design Cross-sectional study. PATIENTS AND METHODS We included 112 patients with TBI, hospitalized for at least 3 days and duration of follow-up >1 year after TBI from five (neurosurgical) referral centers. Evaluation of pituitary function included fasting morning hormone measurements and insulin tolerance test (n=90) or, when contraindicated, ACTH stimulation and/or CRH stimulation tests and a GH releasing hormone-arginine test (n=22). Clinical evaluation included quality of life questionnaires. RESULTS We studied 112 patients (75 males), with median age 48 years and mean body mass index (BMI) 26.7±4.8 kg/m(2). Mean duration of hospitalization was 11 (3-105), and 33% of the patients had a severe trauma (Glasgow Coma Scale <9) after TBI. The mean duration of follow-up was 4 (1-12) years. Hypopituitarism was diagnosed in 5.4% (6/112) of patients: severe GH deficiency (n=3), hypogonadism (n=1), adrenal insufficiency (n=2). Patients diagnosed with pituitary insufficiency had significantly higher BMI (P=0.002). CONCLUSION In this study, the prevalence of hypopituitarism during long-term follow-up after TBI was low. Prospective studies are urgently needed to find reliable predictive tools for the identification of patients with a significant pre-test likelihood for hypopituitarism after TBI.

Nutrition and the circadian timing system

Life on earth has evolved under the daily rhythm of light and dark. Consequently, most creatures experience a daily rhythm in food availability. In this review, we first introduce the mammalian circadian timing system, consisting of a central clock in the suprachiasmatic nucleus (SCN) and peripheral clocks in various metabolic tissues including liver, pancreas, and intestine. We describe how peripheral clocks are synchronized by the SCN and metabolic signals. Second, we review the influence of the circadian timing system on food intake behavior, activity of the gastrointestinal system, and several aspects of glucose and lipid metabolism. Third, the circadian control of digestion and metabolism may have important implications for several aspects of food intake in humans. Therefore, we review the human literature on health aspects of meal timing, meal frequency, and breakfast consumption, and we describe the potential implications of the clock system for the timing of enteral tube feeding and parenteral nutrition. Finally, we explore the connection between type 2 diabetes and the circadian timing system. Although the past decade has provided exciting knowledge about the reciprocal relation between biological clocks and feeding/energy metabolism, future research is necessary to further elucidate this fascinating relationship in order to improve human health.

Low Bone Mineral Density in Patients With Well-Suppressed HIV Infection: Association With Body Weight, Smoking, and Prior Advanced HIV Disease

BACKGROUND Human immunodeficiency virus (HIV) and combination antiretroviral therapy (cART) may both contribute to the higher prevalence of osteoporosis and osteopenia in HIV-infected individuals. METHODS Using dual-energy X-ray absorptiometry, we compared lumbar spine, total hip, and femoral neck bone mineral density (BMD) in 581 HIV-positive (94.7% receiving cART) and 520 HIV-negative participants of the AGEhIV Cohort Study, aged ≥45 years. We used multivariable linear regression to investigate independent associations between HIV, HIV disease characteristics, ART, and BMD. RESULTS The study population largely consisted of men who have sex with men (MSM). Osteoporosis was significantly more prevalent in those with HIV infection (13.3% vs 6.7%; P<.001). After adjustment for body weight and smoking, being HIV-positive was no longer independently associated with BMD. Low body weight was more strongly negatively associated with BMD in HIV-positive persons with a history of a Centers for Disease Control and Prevention class B or C event. Interestingly, regardless of HIV status, younger MSM had significantly lower BMD than older MSM, heterosexual men, and women. CONCLUSIONS The observed lower BMD in treated HIV-positive individuals was largely explained by both lower body weight and more smoking. Having experienced symptomatic HIV disease, often associated with weight loss, was another risk factor. The low BMD observed in younger MSM remains unexplained and needs further study.