An example of a hormone derived from tryptophan is melatonin, which is secreted by the pineal gland and functions in regulating circadian rhythms. Typically, the original structure of the amino acid is modified such that a –COOH, or carboxyl, group is removed, whereas the −NH 3 +, or amine, group remains.Īmine hormones are synthesized from the amino acids tryptophan or tyrosine. Hormones derived from the modification of amino acids are referred to as amine hormones. Figure 17.2.1: Amine, Peptide, Protein, and Steroid Hormone Structure Amine Hormones These chemical groups affect a hormone’s distribution, the type of receptors it binds to, and other aspects of its function. The hormones of the human body can be structurally divided into three major groups: amino acid derivatives (amines), peptides, and steroids ( Figure 17.2.1). Stimulate development of female secondary sex characteristics and prepare the body for childbirth Stimulates development of male secondary sex characteristics and sperm production Stimulates uterine contractions during childbirth Stimulates hormone release by adrenal cortex Endocrine Glands and Their Major Hormones (Table 17.2) The major hormones of the human body and their effects are identified in Table 17.2. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. However, a hormone will only affect the activity of its target cells that is, cells with receptors for that particular hormone. When released into the blood, a hormone circulates freely throughout the body.
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