HORMONES

ENDOCRINE SYSTEM

Name some endocrine glands that are actually divided into two endocrine

glands with different functions; name the hormone(s) they secrete, identify the target organ of each hormone, and the effect of each hormone.

A. Pituitary Gland

1. Anterior Pituitary Gland

 Growth Hormone (GH) - controls growth of the body, targets the bone, muscle 

     and adipose tissue

Thyroid Stimulating Hormone (TSH) - controls the secretion of hormones by the thyroid gland

Follicular cells - secretes thyroid hormone (amine); T4 & T3 (Thyroxin & Triiodothyronine), 
which regulate metabolism.

Parafollicular cells - secretes calcitonin (peptide), release is triggered by an increase in blood calcium levels; targets bone cells by inhibiting osteoclast activity, which in result, causes a decrease in blood calcium and phosphate levels to normal.

 Adrenocorticotropic Hormone or Corticotropin (ACTH) - controls the secretion of hormones by the adrenal cortex; targets the outer portion of the adrenal gland

 Prolactin (PRL) - stimulates the production of milk by the mammary glands

 Follicle Stimulating Hormone - the response depends upon sex, in females, it stimulates maturation of ovum and ovarian follicle; in males, stimulates the maturation of sperm in the testes.

 Luteinizing Hormone (LH) - the response depends upon sex, in females, it causes ovulation; in males, it causes secretion of testosterone.
2. Posterior Pituitary Gland

 Anti-Diuretic Hormone (ADH) or  Vasopressin - targets the kidney tubules; causes the reabsorption of water back to bloodstream and therefore controls water balance and blood pressure

 Oxytocin (OT) - targets uterine smooth muscle and breasts, causes uterine muscle contraction and milk production.

B. Adrenal Gland

1. Adrenal cortex - produces steroid hormones; 

aldosterone, regulates water and electrolyte levels in blood; 

cortisol, regulates glucose metabolism.
2. Adrenal medulla - produces two closely related hormones which function in the sympathetic division of the autonomic nervous system, causing increase in heart rate and blood pressure, muscle contraction, and increase in breathing; epinephrine and norepinephrine

Name the "master" of the anterior pituitary gland.

     The pituitary gland is an endocrine gland. It is one part of a special messenger system, helping to regulate a wide variety of the body functions. The pituitary gland helps to control the body's functions by releasing hormones (special chemical messengers) into the bloodstream.

     The pituitary gland is often called the master gland because it controls several other hormone-releasing gland such as the ovaries, adrenals, and testes. However, the hypothalamus governs the anterior pituitary gland, and is considered as the master of the anterior pituitary gland.

      The hypothalamus receives information from many sources about the basic functions of your body. It uses the information it receives to help regulate these functions. One of the ways the hypothalamus does this involves controlling the pituitary gland. The hypothalamus does this by using its own hormones to communicate with the pituitary gland.

Define the term gonadotropin, name the two gonadotropins secreted by the anterior pituitary

gland, and distinguish between them according to their actions.

                  A gonadotropin is one of a group of protein hormones considered vital to human reproduction. These 

are produced by cells called gonadotropes located in the pituitary gland. The two type of gonadotropin 

are the luteinizing hormone (LH) and follicle stimulating hormone (FSH). Another type of gonadotropin 

is the human chorionic gonadotropin (hCG), which is produced during pregnancy.

Luteinizing Hormone

 In females, ovulation of mature follicles on the ovary is induced by a large burst of LH secretion known as the preovulatory LH surge. Residual cells within ovulated follicles proliferate to form corpora lutea, which secrete the steroid hormones, progesterone and estradiol.

Progesterone is necessary for maintenance of pregnancy, and, in most mammals, LH is required for continued development and function of corpora lutea.The name luteinizing hormone derives from this

effect of inducing luteinization of ovarian follicles.

Follicle-Stimulating Hormone

As its name implies, FSH stimulates the maturation of ovarian follicles. Administration of FSH to humans and animals induces "superovulation", or development of more than the usual number of mature 

follicles and hence, an increased number of mature gametes.

FSH is also critical for sperm production. It supports the function of Sertoli cells, which in turn support many aspects of sperm cell maturation

Explain how the posterior pituitary gland does not produce hormones, but does secrete them.

Posterior Pituitary Gland

The posterior lobe does not produce hormones per se; this is done by the nerve cells in the hypothalamus, but it does not release them into circulation.

ADH and oxytocin are produced in neuronal cell bodies of the supraoptic and paraventricular nuclei in the hypothalamus. They are then transported along the axons of the hypothalamo-hypophyseal tract to the posterior pituitary, where they are stored. Later they are released into the capillary plexus of the infundibular process which passes the hormones to the posterior hypophyseal portal veins for distribution to target cells in otther tissues. No hormones are actually produced in the posterior pituitary, they are only stored~

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REFERENCES

(1) Chapter 13 Endocrine System. [Internet]. Available from: http://www.mhhe.com/biosci/ap/holehaap/outlines/chapt13.pdf.

(2) The Pituitary Gland. [Internet]. Available from: http://www.patient.co.uk/health/the-pituitary-gland

(3) What is Gonadotropin? [Internet]. Available from: http://www.wisegeek.com/what-is-gonadotropin.htm

(4) Gonadotropins: Luteinizing and Follicle Stimulating Hormones. [Internet]. Available from: http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/hypopit/lhfsh.html

(5) An Overview of the Pituitary Gland. [Internet]. Available from: http://www.endocrineweb.com/endocrinology/overview-pituitary-gland

(6) Pituitary Gland. [Internet]. Available from: http://homepage.smc.edu/wissmann_paul/intranetstuff/dept/scienceLRC/wissmann_site/pituitary.htm

(7) W.R Jacinto. Reproductive Cycle (Powerpoint Presentation)