Endocrine Health

HYPOTHALAMIC RELEASING AND INHIBITING HORMONES THAT REGULATE THE ANTERIOR PITUITARY:

(Hormone-->Principal Effects)

Thyrotropin-releasing hormone (TRH)-->Promotes secretion of thyroid-stimulating hormone (TSH) and prolactin (PRL).

Corticotropin-releasing hormone (CRH)-->

Promotes secretion of adrenocorticotropic hormone (ACTH).

Gonadotropin-releasing hormone (GnRH)-->

Promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Growth hormone−releasing hormone (GHRH)-->

Promotes secretion of growth hormone (GH).

Prolactin-inhibiting hormone (PIH)-->Inhibits secretion of prolactin (PRL).

Somatostatin-->Inhibits secretion of growth hormone (GH) and thyroid-stimulating hormone (TSH).

ANTERIOR PITUITARY(ADENOHYPOPHYSIS):

(Hormone-->Target Organ/Tissue-->Effect.)

Follicle-stimulating hormone (FSH)-->Ovaries, testes-->

Female: Growth of ovarian follicles and secretion of estrogen. Male: Sperm production.

Luteinizing hormone (LH)-->Ovaries, testes-->

Female: Ovulation, maintenance of corpus luteum

Male: Testosterone secretion.

Thyroid-stimulating hormone (TSH)-->Thyroid gland-->

Growth of thyroid, secretion of thyroid hormone.

Adrenocorticotropic hormone (ACTH)-->Adrenal cortex-->Growth of adrenal cortex, secretion of glucocorticoids.

Prolactin (PRL)-->Mammary glands, testes-->Female: Milk synthesis. Male: Increased LH sensitivity.

Growth hormone (GH)-->Liver, bone, cartilage, muscle, fat-->Widespread tissue growth, especially in the stated tissues.

POSTERIOR PITUITARY(NEUROHYPOPHYSIS):

(Hormone-->Target Organ/Tissue-->Effect.)

Antidiuretic hormone (ADH)-->Kidneys-->Water retention.

Oxytocin (OT)-->Uterus, mammary glands-->Labor contractions, milk release; possibly involved in ejaculation, sperm transport, sexual affection, and mother−infant bonding.

The Endocrine System is a widespread transport system within the human body. It is primarily concerned with the production and secretion of hormones, which are then circulated throughout the body via the bloodstream. Now, observe how the Endocrine System can relate to you...

FOR THE BODY BUILDER:

Growth Hormone (GH) and growth hormone-inhibiting hormone (GHIH or Somatostatin), along with Testosterone, are the primary hormones involved with tissue and muscular development. Growth Hormone is secreted by the Anterior Pituitary (AP), but that is not the beginning. In the hypothalamus, growth-hormone-releasing-hormone (GHRH) is made, and then secreted into the hypophyseal portal system. This network of blood vessels connects the hypothalamus to the anterior pituitary, thus allowing (GHRH) to activate (GH). In a similar fashion gonadotropin-releasing hormone (GRH) secretion from the hypothalamus triggers the AP to secrete Luteinizing hormone (LH), which is then utilized in males to produce testosterone in the Testicles.

FOR THE ADRENALINE JUNKY AND/OR STRESSED:

Stress, both long-term and short-term, is highly involved with the endocrine system. When talking about the adrenaline junky who seeks a short-term thrill, they are tapping into their ability to secrete the hormones: Epinephrine and Norepinephrine. The hypothalamus sends an efferent nerve signal that reaches the medulla of the adrenal gland, thus secreting the hormones. These hormones enter the bloodstream very quickly, and are then received by target organs. In this instance, heart rate rises, vessels vasodialate, blood pressure rises, and digestion decreases to save energy.

On the other side of the spectrum, long-term stress involves the hypothalamic release of corticotropin-releasing hormone (CRH), which then signals the AP to secrete adrenocorticotropin hormone (ACTH). This active hormones enters the bloodstream and binds to target cells in the adrenal cortex. The three layers of the cortex are the zona glomerulosa, zona fasciculata, and zona reticularis. The z. glomerulosa releases mineralicorticoids (Ex: aldosterone), which is involved with sodium retention as well as water reabsorption. The z. fasciculata secretes glucocorticoids (Ex: cortisol), which initiate lipolysis, gluconeogenesis, and suppresses the immune system with its anti-inflammatory properties. Lastly, the z. reticularis secretes androgens such as DHEA testosterone.

FOR THE SOON-TO-BE PARENTS:

Beginning in the hypothalamus, the secretion of gonadotropin-releaing hormone (GRH), prolactin-releasing hormone (PRH), and prolactin-inhibiting hormone (PIH) signal the AP to release sex-related hormones. Follicle stimulating hormone (FSH) is involved with the maturation of gametes. Luteinizing hormone (LH) is involved with ovulation as well as testosterone secretion as previously stated. Prolactin (PRL) works to synthesis milk in women and increase (LH) sensitivity in men. Another interesting mechanism is that of the posterior pituitary (PP). The hypothalamus connects to it via nerve tracks, and allows for the secretion of oxytocin (OT) which encompasses: labor contractions, milk secretion, mother-infant bonding in women, and ejaculation in men

APPLICABLE INFO FOR CHILDREN The Pineal gland, which secretes melatonin at night, and seratonin in the day is important for sleep function. Therefore, if you are planning on having a child, know that a darker room will induce sleep. Another gland useful to young children is the the Thymus gland. This gland is involved with immunity and fighting infection. Lastly, it should be known that both glands stated previously acquire involution, which means the organ shrinks with age (relative to the size of the human), and is therefore less vital as a child progresses in development.

METABOLISM:

As you may have anticipated, metabolism starts in the hypothalamus with the secretion of thyrotropin-releasing hormone (TRH). Once up-taken in the AP, thyroid-stimulating hormone (TSH) is secreted and then utilized by the thyroid gland. The thyroid then secretes either T3 or T4. The numbers represent the number of iodine molecules on the structure. T3 is the more active form, while T4 has a longer half-life and is more stable. These molecules help regulate the body's metabolism and not enough of these leads to a swollen thyroid as a result of insufficient amounts of Iodine.

On a similar note, the parathyroid gland is in a constant negative feedback loop that revolves around blood calcium levels. When blood calcium is low, parathyroid hormone (PTH) is secreted, which breaks down bone to obtain calcium. Its antagonist is calcitonin, which is secreted by C cells, and works to deposit calcium into the bones when blood calcium is too high.

SUGAR:

Another negative feedback loop within the endocrine system is one that deals with blood glucose levels. After a meal blood glucose rises, which causes beta-cells to secrete insulin from the pancreas' islets Insulin is a protein that binds to cells and allows them to accept glucose molecules, which in return lowers blood glucose levels. In a cyclic manner, when blood glucose is too low, alpha-cells from the pancreas' islets secrete glucagon. This peptide hormone promotes gluconeogenesis, thus taking glucose stores and secreting the molecule into the blood to elevate glucose levels.

As many of you may already know, Diabetes is a disease involving blood glucose and insulin. In Type 1, the individual has a hereditary on set for the inability to secrete insulin. In Type 2, insulin is secreted, however the cell's receptors have either become desensitized or ineffective.

THE BASICS:

Hormones are produced and secreted by glands.
Hormones are received by target-cells
Hormones travel in the bloodstream
Hormones are capable of widespread effects and their effects take longer to initiate compared to the nervous system, but they also last longer in the body.

MAJOR ORGANS/GLANDS:

Hypothalamus
Pineal gland
Pituitary gland
Thymus
Thyroid
Parathyroid
Testes/Ovaries
Adrenal gland
Liver
Kidneys
Pancreas
Mammary gland