The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as hormones. The endocrine system is instrumental in regulating metabolism, growth, development and puberty, tissue function, and also plays a part in determining mood.[1] The field of medicine that deals with disorders of endocrine glands is endocrinology, a branch of the wider field of internal medicine.
Function
The Endocrine system is an information signal system much like the nervous system. However, the nervous system uses nerves to conduct information, whereas the endocrine system mainly uses blood vessels as information channels. Glands located in many regions of the body release into the bloodstream specific chemical messengers called hormones. Hormones regulate the many and varied functions of an organism, e.g., mood, growth and development, tissue function, and metabolism, as well as sending messages and acting on them.
Types of signaling
The typical mode of cell signaling in the endocrine system is endocrine signaling. However, there are also other modes, i.e., paracrine, autocrine, and neuroendocrine signaling [2]. Purely neurocrine signaling between neurons, on the other hand, belongs completely to the nervous system.
Endocrine
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A number of glands that signal each other in sequence is usually referred to as an axis, for example the Hypothalamic-pituitary-adrenal axis.
Typical endocrine glands are the pituitary, thyroid, and adrenal glands. Features of endocrine glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones. In contrast exocrine glands such as salivary glands, sweat glands, and glands within the gastrointestinal tract tend to be much less vascular and have ducts or a hollow lumen.
Autocrine
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Other signaling can target the same cell.
Paracrine
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Paracrine signaling is where the target cell is nearby.
Juxtacrine
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Juxtacrine signals are transmitted along cell membranes via protein or lipid components integral to the membrane and are capable of affecting either the emitting cell or cells immediately adjacent.
Role in disease
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Diseases of the endocrine system are common,[3] including diseases such as diabetes mellitus, thyroid disease, and obesity. Endocrine disease is characterised by dysregulated hormone release (a productive Pituitary adenoma), inappropriate response to signalling (Hypothyroidism), lack or destruction of a gland (Diabetes mellitus type 1, diminished erythropoiesis in Chronic renal failure), or structural enlargement in a critical site such as the neck (Toxic multinodular goitre). Hypofunction of endocrine glands can occur as result of loss of reserve, hyposecretion, agenesis, atrophy, or active destruction. Hyperfunction can occur as result of hypersecretion, loss of suppression, hyperplastic, or neoplastic change, or hyperstimulation.
Endocrinopathies are classified as primary, secondary, or tertiary. Primary endocrine disease inhibits the action of downstream glands. Tertiary endocrine disease is associated with dysfunction of the hypothalamus and its releasing hormones.
Cancer can occur in endocrine glands, such as the thyroid, and hormones have been implicated in signalling distant tissues to proliferate, for example the Estrogen receptor has been shown to be involved in certain breast cancers. Endocrine, Paracrine, and autocrine signalling have all been implicated in proliferation, one of the required steps of oncogenesis.[4]
Table of endocrine glands and secreted hormones
This is a table of the glands of the endocrine system, and their secreted hormones
Oxytocin and Anti-Diuretic Hormone are not secreted in the posterior lobe, merely stored.
| Secreted hormone |
From cells |
Effect |
| Calcidiol (25-hydroxyvitamin D3) |
|
Inactive form of Vitamin D3 |
These originate either from the ovarian follicle or the corpus luteum.
See also
External links
References
- ^ Collier, Judith. et.al (2006). Oxford Handbook of Clinical Specialties 7th edn.. Oxford, 350 -351. ISBN 0-19-853085-4.
- ^ University of Virginia - HISTOLOGY OF THE ENDOCRINE GLANDS
- ^ Kasper et al. (2005). Harrison's Principles of Internal Medicine. McGraw Hill, 2074. ISBN 0-07-139140-1.
- ^ Bhowmick NA, Chytil A, Neilson EG, Moses HL (2004). "TGF-beta signaling in fibroblasts modulates the oncogenic potential of adjacent epithelia.". Science Feb 6 303(5659): 848-51. doi:10.1126/science.1090922.
- ^ Kosfeld M et al. (2005) Oxytocin increases trust in humans. Nature 435:673-676. PDF PMID 15931222
- ^ Scientific American Mind, "Rhythm and Blues"; June/July 2007; Scientific American Mind; by Ulrich Kraft
- ^ a b c Kaushansky K. Lineage-specific hematopoietic growth factors. N Engl J Med 2006;354:2034-45. PMID 16687716.
- ^ The adipose tissue as a source of vasoactive factors. Frühbeck G. (Curr Med Chem Cardiovasc Hematol Agents. 2004 Jul;2(3):197-208.)
- ^ http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/somatostatin.html Colorado State University - Biomedical Hypertextbooks - Somatostatin
- ^ Diabetes-related changes in contractile responses of stomach fundus to endothelin-1 in streptozotocin-induced diabetic rats Journal of Smooth Muscle Research Vol. 41 (2005) , No. 1 35-47. Kazuki Endo1), Takayuki Matsumoto1), Tsuneo Kobayashi1), Yutaka Kasuya1) and Katsuo Kamata1)
- ^ a b Physiology at MCG 5/5ch4/s5ch4_17
- ^ Pentikäinen V, Erkkilä K, Suomalainen L, Parvinen M, Dunkel L. Estradiol Acts as a Germ Cell Survival Factor in the Human Testis in vitro. The Journal of Clinical Endocrinology & Metabolism 2006;85:2057-67 PMID 10843196
- ^ a b c d Placental Hormones
- ^ Physiology at MCG 5/5ch9/s5ch9_13
- ^ Hould F, Fried G, Fazekas A, Tremblay S, Mersereau W (1988). "Progesterone receptors regulate gallbladder motility". J Surg Res 45 (6): 505-12. PMID 3184927.
- ^ Hormonal Therapy
- ^ Massaro D, Massaro GD (2004). "Estrogen regulates pulmonary alveolar formation, loss, and regeneration in mice". American Journal of Physiology. Lung Cellular and Molecular Physiology 287 (6): L1154-9. PMID 15298854 doi= 10.1152/ajplung.00228.2004.
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Endocrine system: hormones/endocrine glands (Peptide hormones, Steroid hormones) |
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| Hypothalamic-pituitary |
Hypothalamus: TRH, CRH , GnRH, GHRH, somatostatin, dopamine - Posterior pituitary: vasopressin, oxytocin - Anterior pituitary: α ( FSH, LH, TSH), GH, prolactin, POMC ( ACTH, MSH, endorphins, lipotropin)
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| Adrenal axis |
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| Thyroid axis |
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| Gonadal axis |
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| Other end. glands |
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| Non-end. glands |
Placenta: hCG, HPL, estrogen, progesterone - Kidney: renin, EPO, calcitriol, prostaglandin - Heart atrium: ANP - Stomach: gastrin, ghrelin - Duodenum: CCK, GIP, secretin, motilin, VIP - Ileum: enteroglucagon - Adipose tissue: leptin, adiponectin, resistin - Thymus: Thymosin - Thymopoietin - Thymulin - Skeleton: Osteocalcin - Liver/other: Insulin-like growth factor ( IGF-1, IGF-2)
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| Target-derived |
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