What Is Pituitary Growth Hormone?

Pituitary hormones (hypophyseal hormones, pituitaryhormones) are a general term for a variety of trace protein and peptide hormones secreted by the vertebrate pituitary (or pituitary). They have different functions, and regulate the growth, development, reproduction, metabolism of the animal body, or control the activities of peripheral endocrine glands and organs.

Pituitary hormone

The pituitary gland consists of the pituitary gland (the anterior and middle lobe) and the posterior lobe of the neural pituitary.

Anterior pituitary hormones that have been identified for function and structure include:

Thyroid stimulating hormone (TSH)

A glycoprotein hormone composed of two peptide chains (or subunits) of and through non-covalent bonds. TSH is the same as the -subunit of gonadotrophins, but the -subunits are different. It promotes thyroid hyperplasia, strengthens the gland's synthesis and secretes thyroid hormones. When the secretion of thyroid hormone in the body is insufficient, the negative feedback effect on the anterior pituitary gland is released, and TSH secretion is enhanced, leading to

Posterior pituitary hormones include oxytocin and vasopressin, both are nonapeptide amides with a disulfide bond. Oxytocin stimulates the strong contraction of uterine smooth muscle and the contraction of mammary epithelial cells, causing the secretion of milk. Medicine is mainly used for induction of labor, postpartum uterine contraction and postpartum hemostasis. Vasopressin, also known as antidiuretic hormone (ADH), acts on the kidneys and regulates the balance of water and salt and the osmotic pressure of body fluids. It has antidiuretic effects and can cause blood pressure to rise at higher concentrations. When there is a lot of bleeding, its blood pressure regulating effect is more important. It is used medically to treat diabetes insipidus, and is used as a hemostatic agent in massive hemoptysis.

figure 1

During biological evolution, mutations in individual bases and gene duplication in DNA cause divergent differentiation of polypeptide molecules. Any mutated molecule can transmit information between the secretory cell (the place it is produced) and the effector cell (the object that it acts on), causing an echoing relationship, and is conducive to coordinating the dynamic balance of metabolism in the body and adapting to the external changes , It gradually develops into the polypeptide hormone of the offspring. Progeny products often retain certain structural features and weak inherent biological effects of ancestral molecules. Receptor protein molecules are also evolving.

figure 2

When the organism evolves to sensitively receive the release signal of an existing peptide hormone, the hormone begins to acquire new functions. For example, the chemical structure of oxytocin and vasopressin in vertebrates is similar. The former is shown in Figure 1 and the latter is shown in Figure 2. The mutation position is the third and eighth positions. Structural variation leads to functional differentiation, but oxytocin has weak vasopressin activity and vice versa. The original vertebrate lamprey was only oxytocin, the ancestral molecule of oxytocin and vasopressin. Its points

image 3

The substructure is shown in Figure 3.

The first half looks like oxytocin, and the second half looks like vasopressin. It has both the biological activity of oxytocin and vasopressin, but the titer is halved. After hundreds of millions of years of evolution, from aquatic fish to amphibians, and then gradually to terrestrial mammals, due to the regulation of water and salt metabolism in the body, spawning, childbirth, nurturing and other processes and the organs involved in the regulation are more The shape is complicated, and then differentiated from oxytocin and oxytocin and vasopressin. Similar examples are common in pituitary hormones. For example, growth hormone and prolactin are similar in structure and functionally differentiated, but they also have overlapping physiological effects. Compared with gonadotropin, TSH has the same -subunit and the obvious difference in -subunit structure, which leads to physiological function differentiation. The same sequence of fragments appeared in ACTH and -LPH molecules, and both of them were degraded from a common precursor-opioid peptide-melanotrophin-procorticoid (POMC). Multiple repeat sequences are contained in the same precursor, suggesting that molecular evolution is the result of cumulative effects of gene duplication, gene fragment fusion, and gene mutation.