Free Essay: An Overview of the sex Hormone Binding Globulin
Sex hormone binding globulin is a glycoprotein that binds itself to androgen, estrogen and sex hormones. It is also referred to as the sex-steroid binding globulin and is found in all vertebrate living creatures except birds. However, the sex hormone binding globulin does not bind steroid hormones such as cortisol, progesterone or other corticosteroids. These are bound by transcortin.
Structure of the sex hormone binding globulin
The sex hormone binding globulin is mainly produced by the liver. It can also be produced by the uterus, placenta, testes and the brain before being released into the bloodstream. Where the testes produce sex hormone binding globulin, the result is androgen-binding proteins.
There is a specific gene that carries the sex hormone binding globulin and this is found on chromosome 17 and is called the Shbg. Structurally, the sex hormone binding globulin has two identical peptide chains which make it homodimeric. Even though it has the same amino acid sequence androgen binding protein, they have different oligosaccharides are also produced in different parts of the body.
In addition, the sex hormone binding globulin has double laminin domains. These G-like domains form pockets which bind hydrophobic molecules. These pocket like domains contain a serine residue which attracts two different types of steroids at differing intervals. This changes the orientation of the steroids in the domains.
The sex hormone binding globulin also has calcium ion which is necessary for linking two elements of a dimer together. Where part of the peptide chain forming the sex hormone binding globulin is disorganized, a zinc ion is used in orientating it.
The role of sex hormone binding globulin
The sex hormone binding globulin is used in transportation of the sex hormones such as testosterone and estradiol through the blood stream. The sex hormones are attached to the sex hormone binding globulin and transported to the right places. It can also be used in inhibiting or enhancing the production of sex hormones. Inhibition and enhancement depend on the amount of certain substances in the body. For instance, an increase in thyroxine and estrogen can lead to high levels of the sex hormone binding globulin. On the other hand, prolactin, transcortin, insulin, growth hormone and androgens can lower the levels of the sex hormone binding globulin. There are also certain conditions that can trigger decrease or increase in the sex hormone binding globulin.
Conditions such as obesity, hypothyroidism, acromegaly, polycystic ovary syndrome and Cushing’s syndrome can reduce levels of the sex hormone binding globulin. Puberty also reduces these levels with boys experiencing a much lower level of the sex hormone binding globulin as compared to girls. Anorexia nervosa, hyperthyroidism, pregnancy, oral contraceptives, certain drugs and cirrhosis can increase the sex hormone binding globulin levels in the body. There are different effects of high or low levels of the sex hormone binding globulin. For instance people with very low levels of this hormone binding globulin have high risk of getting type 2 diabetes. Tests can always be done to determine the levels in the body.
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