Structural Biochemistry/Hormones

Steroid and Thyroid hormones


Both of them are hormones which are lipid soluble. These hormones can pass across the cell membrane and enter into cytosol or even the nucleus. Cholesterol is the single precursor molecule for Steroid hormones. The estrogens (female sex hormones) and androgens (male sex hormones) are two classes of steroid hormones. Estrogen can diffuse across the membrane of a target cell and interact with a specific receptor with the cytoplasm. After forming of steroid-receptor complex, it can pass through nucleus membrane and enter into the nucleus. In the nucleus, it changes the transcription of mRNA for certain protein.

Thyroid hormones can regulate growth. Also it can play a role in stimulating the breakdown of proteins, fats, and glucose. Thyroid hormone secreted from the thyroid gland. They similarly diffuse across the plasma membrane and get into the nucleus. The thyroid-receptor complex influences certain transcription essential for some metabolic processes.

Differences Between Androgen and Estrogen
Firstly, a hormone is produced chemically through the endocrine gland and possesses a specific effect on the activities of various organs in the body. Specific activities with which hormones help are growth and development, sexual function, reproduction, mood, and metabolism. The major endocrine glands through which hormones are produced are the pituitary, pineal, thymus, pancreas, thymoid, and adrenal glands. The primary male and female hormones are called the androgen and the estrogen. Males can produce these hormones in the testes, while women produce them in the ovaries. Although males and females possess both of these types of hormones, they possess them in significantly different amounts. For instance, the majority of males produce an immense amount testosterone, a form of an androgen, whereas women barely produce any amount. This relationship is the same with a male possessing levels of estrogen. Males still do produce this hormone, but in extremely small amounts daily.

Androgen: They are a group of hormones that play a role in male characteristic traits and reproductive activity. It is also considered a steroid, such as testosterone, that regulates the development of masculine characteristics. The male characteristics that androgens help develop include secondary sex characteristics that boys develop when going through puberty. Also, androgens influence sperm-cell formation and sexual interest and behavior. Androgens may be called "male hormones." Both men's and women's bodies produce androgens, just in differing amounts. In fact, androgens have more than 200 actions in women. The principal androgens are testosterone and androstenedione. They present in much higher levels in men. Other androgens include dihydrotestosterone (DHT), dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S). In a woman's body, one of the main purposes of androgens is to be converted into the female hormones called estrogens. In women, androgens are produced in the ovaries, adrenal glands and fat cells. In fact, women may produce too much or too little of these hormones-disorders of androgen excess and deficiency are among the more common hormonal disorders in women. In women, androgens play a key role in the hormonal cascade that kick-starts puberty, stimulating hair growth in the pubic and underarm areas. Additionally, these hormones are believed to regulate the function of many organs, including the reproductive tract, bone, kidneys, liver and muscle. In adult women, androgens are necessary for estrogen synthesis and have been shown to play a key role in the prevention of bone loss, as well as sexual desire and satisfaction. They also regulate body function before, during and after menopause.

About Androgen-Related Disorders: a) High Androgen Levels Excess amounts of androgens can pose a problem, resulting in such "virilizing effects" as acne, hirsutism (excess hair growth in "inappropriate" places, like the chin or upper lip) and thinning hair. Many women with high levels of a form of testosterone called "free" testosterone have polycystic ovary syndrome (PCOS), characterized by irregular or absent menstrual periods, infertility, blood sugar disorders, and, in some cases, symptoms like acne and excess hair growth. Left untreated, high levels of androgens, regardless of whether a woman has PCOS or not, are associated with serious health consequences, such as insulin resistance and diabetes, high cholesterol, high blood pressure and heart disease. In addition to PCOS, other causes of high androgen levels (called hyperandrogenism) include congenital adrenal hyperplasia (a genetic disorder affecting the adrenal glands that afflicts about one in 14,000 women) and other adrenal abnormalities, and ovarian or adrenal tumors. Medications such as anabolic steroids can also cause hyperandrogenic symptoms.

b) About Low Androgen Levels: Low androgen levels can be a problem as well, producing effects such as low libido (interest or desire in sex), fatigue, decreased sense of well-being and increased susceptibility to bone disease. Because symptoms like flagging desire and general malaise have a variety of causes, androgen deficiency, like hyperandrogenism, often goes undiagnosed. Low androgen levels may affect women at any age but most commonly occur during the transition to menopause, or "perimenopause," a term used to describe the time before menopause (usually two to eight years). Androgen levels begin dropping in a woman's age of 20, and by the time she reaches menopause, they have declined 50 percent or more from their peak as androgen production declines in the adrenal glands and the midcycle ovarian boost evaporates. Further declines in the decade following menopause indicate ever-decreasing ovarian function. For many women, the effects of this further decline include hot flashes and accelerated bone loss. These effects may not become apparent until the women are in their late 50s or early 60s.

About Treatment for Low Androgen Levels: Combination estrogen/testosterone medications are available for women in both oral and injected formulations. Small studies find they are effective in boosting libido, energy and well-being in women with androgen deficiencies, as well as providing added protection against bone loss. However, the risks from the combination of estrogen and testosterone include increased risk of breast and endometrial cancer, adverse effects on blood cholesterol and liver toxicity. Testosterone is also an effective treatment for AIDS-related wasting and is undergoing studies for treating premenstrual syndrome (PMS) and autoimmune diseases. Women with PMS may have below-normal levels of testosterone throughout the menstrual cycle.

Estrogen: They are the sex hormones produced primarily by a female's ovaries that stimulate the growth of a girl's sex organs, as well as her breasts and pubic hair, known as secondary sex characteristics. Estrogens also regulate the female menstrual cycle.

Estrogen is the general name for a group of hormone compounds. It is the main sex hormone in women and is essential to the menstrual cycle. Although both men and women have this hormone, it is found in higher amounts in women, especially those capable of reproducing. Secondary sex characteristics, which are defining differences between men and women that don't relate to the reproductive system, are determined in part by estrogen. In women, these characteristics include breasts, a widened pelvis, and increased amounts of body fat in the buttock, thigh, and hip region. This hormone also contributes to the fact that women have less facial hair and smoother skin then men. It is also an essential part of a woman's reproductive process. Estrogen regulates the mentrual cycle and prepares the uterus for pregnancy by enriching and thickening the endometrium. Two hormones, the luteinzing hormone (LH) and the follicle stimulating hormone (FSH), help to control how the body produces estrogen in women who ovulate. Estrogen is manufactured mostly in the ovaries, by developing egg follices. Moreover, it produced by the corpus luteum in the ovaries, as well as by the placenta. The liver, breasts and adrenal glands may also contribute to its production, although in smaller quantities. There are three distinct compounds that make up this hormone group: estrone, estradio and estriol. During a woman's reproductive life, which starts with the onset of menstruation and continues until menopause, the main type of estrogen produced is estradiol. Enzymatic actions produce estradiol from androgens. Testosterone contributes to the production of estradio, while the estrone is made from andostenedione.

Estrogen is important to a woman's health beyond just how it relates to her reproductive cycle. Although it can cause women to retain fluid, and early exposure through early menses can increase a woman's risk of developing breast cancer, this hormone has significant benefits.

 Androgens as related to women 

In women, androgens are produced in the adrenal glands, ovaries, and fat cells. Disorders involving excess or inadequate levels of androgens in women constitute many of their common hormonal disorders. For women, the key roles of androgens are to aid in the starting of puberty and to regulate the function of certain organs. For adult women, androgens are needed for estrogen synthesis and are involved in the prevention of bone loss, and in sexual desire and satisfaction

The Three Chemical Classes of Hormones
There are three general classes of hormones characterized by their structure, and not their function. The three categories are:

1. Steroids Steroids are lipids which are formed from cholesterol. Examples include testosterone and cortisol. These hormones are given off by gonads, adrenal cortex, and the placenta. Steroids are natural substances with many different effects in the human body, which begin over several days. The primary use of steroids in health care is to reduce inflammation and other disease symptoms. Steroid inhalers have an important role in reducing deaths from asthma, local steroid injections are useful in treating painful joints and ligaments. Steroid creams are used extensively to treat eczema and other inflammatory skin conditions. Steroids make the whole immune system less active, which can be very useful in illnesses where there is an immune component. Steroids are the ultimate anti-inflammatory drugs. However, steroid use in medicine is limited by very serious side effects in the body as a whole. That is why steroids tend to be used sparingly in local preparations such as sprays and creams, which ensure maximum steroid dose where it is needed, and minimum levels in the blood stream. Steroids also affect the brain, and high doses can make people feel happy, euphoric, hyped-up, with disturbance of sleep and even serious psychiatric illness such as mania, very aggressive behavior and psychosis (delusions, pananoia, loss of touch with reality). If steroid users are also taking other drugs which affect mood or brain function, these side-effects can be far more common. Steroids are really useful in the care of those with advanced cancer when short life expectancy from their condition means physicians are far more relaxed about long term side-effects. Brain tumours often respond dramatically to steroids. The reason is that the brain is contained in a bony box inside the skull and pressure can build up inside the head, resulting in headaches, sickness, drowsiness and other problems. Brain scans often show that a tunour the size of a wallnut can be surrounded by a big immune reaction, with brain swelling and inflammation. Steroids reduce the additional swelling, often reversing symptoms and buying time. The underlying cancer continues to grow if the person finally begins to deteriorate death often follows rapidly as the steroid dose is reduced. So steroids are really powerful, with wide ranges of actions, producing dramatic effects ranging from pain relief to mood elevation, and if it were not for the very serious side effects, they would be used even more often. The body becomes dependent on steroids and when used in health care, most physicians reduce dosage gradually, even though they may start in an acute illness with a very high dose.

2. Peptides

Peptides are the most common type of hormones and contain a chain of amino acids. Examples include TRH and vasopressin. These hormones are given off by the heart, liver, stomach, kidney, pituitary gland, and parathyroid. Peptides play a crucial role in fundamental physiological and biochemical functions of life. For decades now, peptide research is a continuously growing field of science. When the number of amino acids is less than about 50, these molecules are named peptides while larger sequences are referred to as proteins. The amino acids are coupled by a peptide bond, a special linkage in which the nitrogen atom of one amino acid binds to the carboxyl carbon atom of another. Peptides (proteins) are present in every living cell and possess a variety of biochemical activities. They appear as enzymes, hormones, antibiotics, receptors, etc. Synthetic peptides may be useful in structure-function studies of polypeptides, as peptid hormones and hormone analogues, in the preparation of cross-reacting antibodies, and in the design of novel enzymes. Peptides are synthesized by coupling the carboxyl group or C-terminus of one amino acid to the amino group or N-terminus of another. There are two strategies for peptide synthesis: liquid-phase peptide synthesis and solid-phase peptide synthesis (SPPS).

3. Amines Amine-derived hormones are derived from the amino acids tyrosine and tryptophan. Examples include catecholamines and thyroxine. These hormones are given off by the thyroid and adrenal medulla. In amines, the hydrogen atoms in the ammonia have been replaced one at a time by hydrocarbon groups. Amines fall into different classes depending on how many of the hydrogen atoms are replaced. In primary amines, only one of the hydrogen atoms in the ammonia molecule has been replaced. That means that the formula of the primary amine will be RNH2 where "R" is an alkyl group. In a secondary amine, two of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. In a tertiary amine, all of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups.