Pituitary Hormones

Human anatomy > Endocrine System > Pituitary Hormones

The pituitary gland secretes nine important hormones. Seven of these hormones are produced by anterior segment of the gland - one of these is produced by the pars intermedia (the tissue that’s more noticeable in a fetal body). The other two hormones are created by the hypothalamus and secreted by the pituitary, after they have gone through axions and the infundibulum. The posterior segment of the gland then releases the hormones into the bloodstream.

Trophic hormones (to mean food) is secreted by the pars distalis into the bloodstream. They are able to increase the size of the target glands, thus making a seemingly “feeding” action to the glands. Without trophic hormones, the target glands would shrink.

Somatotropin, the growth hormone, is in charge of facilitating the growth of cells and their mitotic activity. Growth hormones are secreted by the hypothalamus in two types: the growth ‘hormone-inhibiting’ hormone and growth ‘hormone-releasing’ hormone, based on cell division. The manner with which the growth hormone releases or inhibits is not totally clear, as well as the manner with which it acts once it’s in the bloodstream. But, it’s clear that the growth hormone has a direct impact on the amino acids of the cells. Also, it shows a direct relationship to the synthesis of protein, as clearly shown by cases of dwarfism and gigantism. There is a noticeable high level of hormone-inhibiting growth hormones. The case with gigantism is the toal opposite, there is a very high level of hormone-releasing growth hormones. When too little secretion is made (hyposecretion) or too much secretion is done (hypersecretion), the body suffers abnormalities of features. Adults bodies normally display joint fusion distortions if any of the above anomalies happen.

The thyrotropin is the hormone that stimulates the thyroid. It is primarily concerned with regulating the functions of the thyroid gland. Another hormone, though, helps the thyrotropin. This is the thyrotropin-releasing hormone, produced by the hypothalamus. The thyrotropin is usually triggered by outside factors like the cold. Another consideration that stimulates it is emotional upheaval or illnesses. The regulation of the adrenal cortex is done by the hormone adrenalcorticotropic. Also assisting in the metabolism of fat in targeted cells, this hormone is produced by the hypothalamus. This hormone, like the thyrotropin, is also stimulated by emotional upheaval.

The follicle-stimulating hormone’s actions vary, based on the gender of the body that it inhabits. The follicle-stimulating hormone in males encourage the testes to secrete a healthy amount of sperm cells. In females, the same hormone takes care of the egg development, the monthly cycle and the production of estrogen. The luteinizing hormone works with the follicle-stimulating hormone. The two hormones are focused on reproductive cells. Also called as the gonadotrophins, they are necessary to the process of reproduction for they stimulate ovulation, and the formation of the corpus luteum (in females). The luteinizing hormone secretes progesterone, too, another vital sex hormone. In the male body, the luteinizing hormone produces testosterone (and it’s called the interstitial cell-stimulating hormone). Not much is known about the other mechanism that manages how the gonadotrophins function. But, it has been speculated that the hormones are released after puberty.

The hormone prolactin is found in both the male and female body. But, it serves a greater part in females by triggering lactation after birth. It works with other hormones so that breast milk would be produced. This hormone is produced by the hypothalamus through the secretion of the prolactin-inhibiting hormone dopamine. Dopamine kicks into action when lactation is needed.

The melanocyte-stimulating hormone is found to darken the skin through its melanin granules found in the melanocytes. Medical science has not shed further light on it except that it’s managed by the hypothalamus. The hypothalamus also makes sure that two regulating hormones would facilitate melanocyte-stimulating hormone secretion (the corticotrophin or the secretion-enhancer and the dopamine which is the secretion-inhibitor.)

Oxytocin is also produced by the hypothalamus. Coming from the specialized cells of the hypothalamus, oxytocin travels by way of the axons of the infundibulum, reaching the lobus nervosa. The lobus nervosa houses the hormone and releases it when the hypothalamus calls for it. Oxytocin (if released) journeys to the female reproductive system and triggers fetal gestation contractions. After birth, this hormone helps with the ejaculation process of the mamary glands and the areola for lactation. A high oxytocin level in the male body has been found to lead to increased ejaculation.

The anti-diuretic hormone goes through the same process as the oxytocin, but it plays an entirely different role. It’s also a polypeptide but it targets the kidney - where it regulates water production. Too high a level of this hormone in the kidneys triggers vasoconstriction, so the anti-diuretic hormone is classified as a vasopressin.

The oxytocin and the anti-diuretic hormone are managed by the posterior pituitary. They’re created in the supraoptic nuclei and paraventricular nuclei of the hypothalamus. These nucleis are known as the endocrine system. The hormones that they secrete use the hypothalamo-hypophyseal tract until they reach the posterior segment of the pituitary gland. The gland keeps them in check until the need for their release is triggered.

Oxytocin and the anti-diuretic hormone are released into the system by the neuroendocrine reflexes. These reflexes depend on external stimuli. For example, a lactating woman needs suckling as a stimuli so that oxytocin may be released by the hypothalamus.

The anti-diuretic hormone is facilitated by a lot of factors and stimuli. The osoreceptor neurons of the hypothalamus are on top of the list. They react to a rise in the blood osmotic pressure that the stretch receptors in the left atrium detects.

The “master gland” is the anterior section of the pituitary gland. It earned that because of the great number of hormones that it secretes, compared to the rest of the endocrine glands. Some of these hormones are the thyroid-stimulating hormone (which looks after the thyroid), the adrenocorticotrophic hormone (which manages the adrenal cortex), and the gonadotrophic hormone (which faciliates the gonads). All of those hormones are dictated by the functioning capability of the anterior pituitary. But, the nickname “master gland” is not entirely correct, because the anterior pituitary still depends on the hypothalamus - which is the true gland that manages secretions and facilitation of hormones and the glands that produce them. The inhibiting or stimulating hormones from the hypothalamus pass by way of the hypothalamo-hypophyseal portal to get to the anterior pituitary. They all enter the median eminence through the primary capillaries network. The anterior pituitary’s secondary capillaries get the venous drainage that comes from the pituitary stalk. Those two types of capillaries network serves as a passage for neuron transport or hormonal transport.

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