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Testosterone—this is secreted by the testes and is a steroid hormone. It stimulates the development of the male secondary sex characteristics and sperm production.
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Estrogen and progesterone—these are steroid hormones that stimulate the development of female secondary sex characteristics and manage the menstrual cycle and pregnancy.
HORMONE TYPES There are several different hormone classifications: steroid hormones, peptide hormones, amine hormones, protein hormones, and glycopeptide hormones. The amine hormone includes norepinephrine, which is a modified amino acid. The oxytocin hormone is an example of a peptide hormone (which is a short amino acid molecule). Growth hormone is a protein hormone (which is a long chain of amino acids). Testosterone is an example of a steroid hormone. Amine hormones are modified amino acids, with removal of the carboxyl group. These are synthesized from tryptophan or tyrosine. An example of a tryptophan-based hormone is melatonin, secreted by the pineal gland. Tyrosine derivatives include the thyroid hormones, epinephrine, norepinephrine, and dopamine. Dopamine is an inhibitory neurotransmitter/hormone that blocks the release of some anterior pituitary hormones. Peptide and protein hormones are all chains of amino acids. The difference between these is the length of the amino acid chain. Both are synthesized by the usual DNA/mRNA and ribosomal protein synthesis channels. Examples of peptide hormones include antidiuretic hormone (ADH) and atrial-natriuretic peptide (which decreases blood pressure and is made by the heart). Some protein-based hormones include growth hormone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Both FSH and LH are called glycoproteins because they have added carbohydrates attached to the protein. Steroid hormones are lipid-derived, made from cholesterol. These include testosterone, estrogen, progesterone, cortisol, and aldosterone. These are not water-soluble so they need to travel via a transport protein. As a result these types of hormones are longer-lasting than 183
