Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. Hormones are molecules that act as signals from one type of cells to another. Most hormones reach their targets via the blood. Although every organ system secretes and responds to hormones (including the brain, lungs, heart, intestine, skin, and the kidney), the clinical specialty of endocrinology focuses primarily on the endocrine organs, meaning the organs whose primary function is hormone secretion. These organs include the pituitary, thyroid, adrenals, ovaries and testes, and pancreas.

An endocrinologist is a doctor who specializes in treating disorders of the endocrine system, such as diabetes, hyperthyroidism, and many others (see list of diseases below). A disease due to a disorder of the endocrine system is often called a "hormone imbalance," but is technically known as an endocrinopathy or endocrinosis.

Background

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All multicellular organisms need “Coordinating systems to regulate and integrate the function of differentiating cells.” Two mechanisms perform this function in higher animals: the nervous system and the endocrine system. The endocrine system acts through the release (generally into the blood) of chemical agents and is vital to the proper development and function of organisms. As Hadley (2000) notes, the integration of developmental events such as proliferation, growth, and differentiation (including histogenesis and organogenesis) and the coordination of metabolism, respiration, excretion, movement, reproduction, and sensory perception depend on “chemical cues, substances synthesised and secreted by the specialised cells within the animal.”

More on [ Endocrinology ]

pubmed: 0013-7227

Biochemical Factors Governing the Steady-State Estrone/Estradiol Ratios Catalyzed by Human 17{beta}-Hydroxysteroid Dehydrogenases Types 1 and 2 in HEK-293 Cells.
Sherbet DP, Guryev OL, Papari-Zareei M, Mizrachi D, Rambally S, Akbar S, Auchus RJ Related Articles Biochemical Factors Governing the Steady-State Estrone/Estradiol Ratios Catalyzed by Human 17{beta}-Hydroxysteroid Dehydrogenases Types 1 and 2 in HEK-293 Cells. Endocrinology. 2009 Jun 25; Authors: Sherbet DP, Guryev OL, Papari-Zareei M, Mizrachi D, Rambally S, Akbar S, Auchus RJ Human 17beta-hydroxysteroid dehydrogenase types 1 and 2 (17betaHSD1, 17betaHSD2) regulate estrogen potency by catalyzing the interconversion of estrone (E1) and estradiol (E2) using nicotinamide adenine dinucleotide (phosphate) cofactors NAD(P)(H). In intact cells, 17betaHSD1 and 17betaHSD2 establish pseudo-equilibria favoring E1 reduction or E2 oxidation, respectively. The vulnerability of these equilibrium steroid distributions to mutations and to altered intracellular cofactor abundance and redox state, however, is not known. We demonstrate that the equilibrium E2:E1 ratio achieved by 17betaHSD1 in intact HEK-293 cell lines is progressively reduced from 94:6 to 10:90 following mutagenesis of R38, which interacts with the 2'-phosphate of NADP(H), and by glucose deprivation, which lowers the NADPH/NADP(+) ratio. The shift to E2 oxidation parallels changes in apparent Km values for purified 17betaHSD1 proteins to favor NAD(H) over NADP(H). In contrast, mutagenesis of E116 (corresponding to R38 in 17betaHSD1) and changes in intracellular cofactor ratios do not alter the >90:10 E1:E2 ratio catalyzed by 17betaHSD2, and these mutations lower the apparent Km of recombinant 17betaHSD2 for NADP(H) only <3-fold. We conclude that the equilibrium E1:E2 ratio maintained by human 17betaHSD1 in intact cells is governed by NADPH saturation, which is strongly dependent on both R38 and high intracellular NADPH/NADP(+) ratios. In contrast, the preference of 17betaHSD2 for E2 oxidation strongly resists alteration by genetic and metabolic manipulations. These findings suggest that additional structural features, beyond the lack of a specific arginine residue, disfavor NADPH binding thus and support E2 oxidation by 17betaHSD2 in intact cells. PMID: 19556422 [PubMed - as supplied by publisher]
Inhibition of NF{kappa}B or Bax prevents Endoplasmic Reticulum Stress- but not Nitric Oxide-mediated Apoptosis in INS-1E cells.
Tonnesen MF, Grunnet LG, Friberg J, Cardozo AK, Billestrup N, Eizirik DL, Størling J, Mandrup-Poulsen T Related Articles Inhibition of NF{kappa}B or Bax prevents Endoplasmic Reticulum Stress- but not Nitric Oxide-mediated Apoptosis in INS-1E cells. Endocrinology. 2009 Jun 25; Authors: Tonnesen MF, Grunnet LG, Friberg J, Cardozo AK, Billestrup N, Eizirik DL, Størling J, Mandrup-Poulsen T Accumulating evidence suggests that endoplasmatic reticulum (ER) stress by mechanisms that include ER Ca(2+) depletion via nitric oxide (NO)-dependent downregulation of SERCA2b contributes to beta-cell death in type 1 diabetes. To clarify if the molecular pathways elicited by NO and ER Ca(2+) depletion differ, we here compare the direct effects of NO, in the form of the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP), with the effects of SERCA2 inhibitor Thapsigargin (TG) on mitogen-activated protein kinases (MAPK), nuclear factor kappaB (NFkappaB), Bcl-2 proteins, ER stress and apoptosis. Exposure of INS-1E cells to TG or SNAP caused caspase-3 cleavage and apoptosis. Both TG and SNAP induced activation of the pro-apoptotic transcription factor C/EBP homologous protein (CHOP). However, other classical ER stress-induced markers such as up-regulation of ER chaperone Bip and alternative splicing of the transcription factor Xbp-1 were exclusively activated by TG. TG exposure caused NFkappaB activation, as assessed by IkappaB degradation and NFkappaB binding to its binding sites. Inhibition of NFkappaB or the Bcl-2 family member Bax pathways protected beta-cells against TG- but not SNAP-induced beta-cell death. These data suggest that NO generation and direct SERCA2 inhibition cause two quantitative and qualitative different forms of ER stress. In contrast to NO, direct ER stress induced by SERCA-inhibition causes activation of ER stress signalling pathways and elicit proapoptotic signalling via NFkappaB and Bax. PMID: 19556421 [PubMed - as supplied by publisher]
Activation of liver X receptor (LXR) regulates substrate oxidation in white adipocytes.
Stenson BM, Rydén M, Steffensen KR, Wåhlén K, Pettersson AT, Jocken JW, Arner P, Laurencikiene J Related Articles Activation of liver X receptor (LXR) regulates substrate oxidation in white adipocytes. Endocrinology. 2009 Jun 25; Authors: Stenson BM, Rydén M, Steffensen KR, Wåhlén K, Pettersson AT, Jocken JW, Arner P, Laurencikiene J Liver X Receptors (LXRs) are nuclear receptors with established roles in cholesterol, lipid and carbohydrate metabolism; although their function in adipocytes is not well characterized. Increased adipose tissue mass in obesity is associated with increased adipocyte lipolysis. Fatty acids (FA) generated by lipolysis can be oxidized by mitochondrial beta-oxidation, re-esterified or released from the adipocyte. The latter results in higher circulating levels of free FAs, in turn causing obesity-related metabolic complications. However, mitochondrial beta-oxidation can at least in part counteract an increased output of FA into circulation. In this study we provide evidence that activation of LXRs upregulates mitochondrial beta-oxidation in both human and murine white adipocytes. We also show that the expression of a kinase regulating the cellular fuel switch, pyruvate dehydrogenase kinase 4 (PDK4), is upregulated by the LXR agonist GW3965 in both in vitro differentiated human primary adipocytes and differentiated murine 3T3-L1 cells. Moreover, activation of LXR causes PDK4-dependent phosphorylation of the pyruvate dehydrogenase complex (PDC), thereby decreasing its activity and attenuating glucose oxidation. The specificity of the GW3965 effect on oxidation was confirmed by RNA interference targeting LXRs. We propose that LXR has an important role in the regulation of substrate oxidation and the switch between lipids and carbohydrates as cellular fuel in both human and murine white adipocytes. PMID: 19556420 [PubMed - as supplied by publisher]
Chorionic gonadotropin regulates prostaglandin E synthase via a PI3K-ERK pathway in a human endometrial epithelial cell line: Implications for endometrial responses for embryo implantation.
Banerjee P, Sapru K, Strakova Z, Fazleabas AT Related Articles Chorionic gonadotropin regulates prostaglandin E synthase via a PI3K-ERK pathway in a human endometrial epithelial cell line: Implications for endometrial responses for embryo implantation. Endocrinology. 2009 Jun 25; Authors: Banerjee P, Sapru K, Strakova Z, Fazleabas AT Successful implantation necessitates modulation of the uterine environment by the embryo for a specific period of time during the menstrual cycle. Infusion of chorionic gonadotropin (CG) into the oviducts of baboons to mimic embryo transit induces a myriad of morphological, biochemical and molecular changes in the endometrium. Endometrial epithelial cells from both baboons and humans when stimulated by CG in vitro, activates a cAMP independent mitogen activated protein kinase (MAPK) pathway leading to prostaglandin E2 (PGE2) synthesis. This study shows that in the human endometrial cell line, HES, CG, acting via its G-protein coupled receptor, phosphorylates protein kinase B (Akt), c-Raf and the extracellular regulatory kinase, ERK1/2 in a phosphatidylinositol 3-kinase (PI3K) dependent manner. Further, ERK1/2 phosphorylation is independent of the signaling paradigms of Galphas, Galphai and epidermal growth factor receptor (EGFR) transactivation, typical of gonadal cells, indicating an alternative signaling pattern in the endometrium. Following phosphorylation by CG, ERK1/2 translocates to the nucleus in a time dependent manner. Downstream of ERK1/2, CG activates the nuclear transcription factor, Elk1, also in a PI3K-MAPK dependent manner. Lastly, we show that in HES cells, this pathway regulates the expression of the microsomal enzyme prostaglandin E synthase (mPTGES), a terminal prostanoid synthase responsible for PGE2 synthesis. CG regulates the mPTGES promoter and also induces mPTGES synthesis in HES cells via the PI3K-ERK1/2 pathway. We suggest that this alternative PI3K-ERK-Elk pathway activated by CG regulates prostaglandin production by the endometrial epithelium and serves as an early trigger to prepare the endometrium for implantation. PMID: 19556419 [PubMed - as supplied by publisher]

pubmed: 0804-4643

Influence of prematurity and growth restriction on the adipokine profile, IGF-I and ghrelin levels in cord blood. Relationship with glucose metabolism.
Martos G, Barrios V, Saenz de Pipaon M, Pozo J, Dorronsoro I, Martinez-Biarge M, Quero J, Argente J Related Articles Influence of prematurity and growth restriction on the adipokine profile, IGF-I and ghrelin levels in cord blood. Relationship with glucose metabolism. Eur J Endocrinol. 2009 Jun 26; Authors: Martos G, Barrios V, Saenz de Pipaon M, Pozo J, Dorronsoro I, Martinez-Biarge M, Quero J, Argente J Objective: To determine the influence of gestational age and fetal growth restriction on the cord blood adipokine profile, IGF-I and ghrelin levels, and their relationship with glucose metabolism. Study design: One hundred and ninety newborns (99 preterm and 91 full term) were studied and, according to their anthropometry at birth, classified as small (SGA) or adequate for gestational age (AGA). Methods: Venous cord blood serum levels of insulin-like growth factor 1 (IGF-I), IGF binding protein 3 (IGFBP-3), adiponectin, resistin, leptin, leptin soluble receptor (sOB-R), tumoral necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), total ghrelin and acylated ghrelin were determined and compared between preterm and full term, as well as between SGA and AGA, newborns. Correlations with newborn weight, gestational age and HOMA index, as an index of insulin resistance, were determined. Results: Preterm newborns had higher HOMA, sOB-R, resistin and IL-6 and lower IGF-I, IGFBP-3, leptin and adiponectin levels than full term newborns. SGA had lower IGF-I, IGFBP-3, leptin, IL-6 and adiponectin and higher sOB-R and total ghrelin than AGA newborns. Adiponectin and HOMA showed independent positive and negative correlations with gestational age, respectively, but not with neonatal weight. Birth weight was correlated positively with IGF-I and leptin levels and negatively with total ghrelin ones. Conclusions: Our findings suggest that the lack of proper acquisition of adipose tissue by the fetus either due to prematurity or to fetal growth restriction is associated with changes in the cord blood adipokine profile that may contribute to the impairment of glucose metabolism. PMID: 19561044 [PubMed - as supplied by publisher]
Restricted thyroglobulin antibody epitope specificities in subjects with type 1 diabetes mellitus.
Okosieme O, Wijeyaratne C, Lazarus J, Premawardhana L Related Articles Restricted thyroglobulin antibody epitope specificities in subjects with type 1 diabetes mellitus. Eur J Endocrinol. 2009 Jun 26; Authors: Okosieme O, Wijeyaratne C, Lazarus J, Premawardhana L Objectives: Following iodisation in Sri Lanka we observed a high prevalence of thyroglobulin antibodies (TgAbs) in type 1 diabetic (T1DM) patients. The clinical significance of these TgAbs is uncertain. We sought to obtain a detailed epitope analysis of TgAbs in T1DM patients recruited from diabetes clinics and to compare these with TgAb epitope specificities in patients with autoimmune thyroid disease (AITD) and healthy individuals in that country. Design and methods: We used a panel of 10 thyroglobulin monoclonal antibodies (Tg-Mabs) in competitive ELISA reactions in a prospective study of subjects recruited from Colombo, to determine the epitopes recognised by TgAb-positive patients with T1DM (n=58, 34F:24M, median age 16 years), AITD patients (n=42, 33F:9M, median age 37 years) and healthy subjects (n=50, 39F:11M, median age 27 years). The outcomes were a comparison of reactivity with 6 Tg clusters (I-VI) in these subjects, and the relation of epitope specificity patterns with free thyroxine (FT4) and TSH. Results: Patients with T1DM and AITD but not healthy control subjects preferentially recognised the immunodominant clusters, I, III and IV. Patients with these narrow epitope specificities had higher median TSH levels (1.60 vs 1.06; P=0.01), and were more frequently positive for TPOAb than those with broad specificities (52.3% vs 7.1%; P=0.004). Conclusions: The TgAb epitope specificities in euthyroid Sri Lankans with T1DM are similar to AITD patients. TgAb epitope studies may potentially identify type 1 diabetic patients at risk of thyroid dysfunction. PMID: 19561043 [PubMed - as supplied by publisher]

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