Lipophilic hormones

Polysorbates and sorbitan esters are used in pharmaceutical emulsions or dispersions containing vitamins or hormones. Lipophilic surfactants such as monoglycerides, propylene glycol ester or sorbitan esters are used as suppository bases. Monoglycerides and other lipophilic surfactants are typical compounds in cosmetic water/oil or oil/water creams, lotions and gels. Hydrophilic surfactants are used to solubilize perfume oils in various cosmetic oils and lotions. 

Their hydroxylated products are more water-soluble than their generally lipophilic substrates, facilitating excretion Liver contains highest amounts, but found In most If not all tissues. Including small Intestine, brain, and lung Located in the smooth endoplasmic reticulum or in mitochondria (steroidogenic hormones)... 

The thyroid hormones are lipophilic and relatively insoluble in the plasma. Therefore, they are transported throughout the circulation bound to plasma proteins such as thyroxine-binding globulin (75%) and albumins (25%). Approximately 99.96% of circulating thyroxine is protein bound. Bound hormone is not available to cause any physiological effects however, it is in equilibrium with the remaining 0.04% that is unbound. This free form of the hormone is able to bind to receptors on target tissues and cause its effects. Thyroid hormone has many metabolic effects in the body ... 

Due to their lipophilic properties, hormones tend to be divided up between the liquid and solid phases, making sorption an important parameter for hormone elimination from the liquid phase of sewage. In laboratory studies based on an... 

The signal is what starts everything off. Signals take a variety of forms, but for our purposes there are only two. The first type are signals that go into the cell, bind to internal receptors, and exert their effects. Steroid hormones, vitamin D, thyroid hormone, and retinoids are the only members of this class. All of the intracellular receptors ultimately activate the transcription of regulated genes. The common feature of signals that enter the cell is that they are all small lipophilic molecules that can cross the cell membrane. 

For an organism to eliminate a lipophilic, chemically inert xenobiotic, it is usually hrst necessary to oxidize it to a more polar form. In addition, many biosynthetic pathways that produce steroid hormones, prostaglandins, leukotrienes, etc. involve oxidative steps. Organisms have evolved many enzymes to carry out these oxidations. Oxidation can occur by addition of oxygen (without addition of hydrogen which would represent hydration), removal of hydrogen atoms (without removal of oxygen which would represent dehydration), or simply removal of electrons. 

H. Bundgaard, J. Mpss, Prodrugs of Peptides. 6. Bioreversible Derivatives of Thyrotropin-Releasing Hormone (TRH) with Increased Lipophilicity and Resistance to Cleavage by the TRH-Specific Serum Enzyme , Pharm. Res. 1990, 7, 885-892. 

S. Muranishi, A. Sakai, K. Yamada, M. Murakami, K. Tanaka, Y. Kiso, Lipophilic Peptides Synthesis of Lauryol Thyrotropin-Releasing Hormone and Its Biological Activity ,... 

Hormones are divided into two major categories, those that are water soluble (hydrophilic) and those that are lipid soluble (lipophilic, also known as hydrophobic). Important properties of these two classes are shown in Table 1-9-1,... 

The conversion of cholesterol to steroid hormones (see p.376) is of minor importance quantitatively, but of major importance in terms of physiology. The steroid hormones are a group of lipophilic signal substances that regulate metabolism, growth, and reproduction (see p.374). 

Depending on the type of hormone, hormone signals are transmitted to the target cells in different ways. Apolar (lipophilic) hormones penetrate the cell and act in the cell nucleus, while polar (hydrophilic) hormones act on the external cell membrane. 

To receive and pass on chemical or physical signals, cells are equipped with receptor proteins. Many of these are integral membrane proteins in the plasma membrane, where they receive signals from their surroundings. Other receptor proteins are located in intercellular membranes. The receptors for lipophilic hormones are among the few that function in a soluble form. They regulate gene transcription in the nucleus (see p. 378). 

Each hormone is the center of a hormonal regulation system. Specialized glandular cells synthesize the hormone from precursors, store it in many cases, and release it into the bloodstream when needed (biosynthesis). For transport, the poorly water-soluble lipophilic hormones are bound to plasma proteins known as hormone carriers. To stop the effects of the hormone again, it is inactivated by enzymatic reactions, most of which take place in the liver (metabolism). Finally, the hormone and its metabolites are expelled via the excretory system, usually in the kidney (excretion). All of these processes affect the concentration of the hormone and thus contribute to regulation of the hormonal signal. 

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