The main hormone binding proteins are SHBG (Sex Hormone Binding Globulin), CBG (Corticosteroid Binding Globulin) and TBG (Thyroxin Binding Globulin). These proteins bind estrogens/androgens, corticosteroids/progesterone, and T3/T4, respectively.

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Monoamine transporters are protein structures that function as integral plasma-membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. Three major classes of MATs (SERT, DAT, NET) are responsible for the reuptake of their associated amine neurotransmitters (serotonin, dopamine, norepinephrine)