Hormones

If you are looking for the one hormone that does this, then the answer is parathyroid hormone (PTH), produced in the parathyroid glands.

A more technical description is given below:

Three hormones act in the body to increase blood calcium levels to normal. These hormones are 1,25-Dihydroxycholecalciferol, parathyroid hormone (PTH), and calcitonin that originate respectively from the liver and kidneys, parathyroid glands, and thyroid glands. The first, 1,25-Dihydroxycholecalciferol (active vitamin D3), serves to increase calcium absorption from the intestine. The second, PTH, dissolves bone into the blood. The third, calcitonin, prevents the bone-derived calcium from being resorbed ("reabsorbed") into the bone from which it came via PTH. To summarize, these three hormones act in concert to raise calcium levels via external and internal routes.

References: Ganong's Review of Medical Physiology, 23eKim E. Barrett, et. al. Chapter 23: Hormonal Control of Calcium & Phosphate Metabolism & the Physiology of Bone

Both norad and adrenaline increases BP, but by different mechanism...

> Adreanaline increases BP by constricting blood vessles

>Noradrenaline Increases BP by increasing HR > Increase Impulse conduction > increase contraction > Increaseing volume expelled> thus increasing BP

> Noradrenaline causes: (i) constriction of the cutaneous vessels; (ii) constriction

of the vessels in skeletal muscle (adrenaline causes transient vasodilatation);

(iii) bradyeardia (adrenaline causes tachycardia); (iv) rise in both

systolic and diastolic pressures (adrenaline causes a rise in systolic pressure and

either does not effect or causes a slight fall in diastolic pressure).

Hormones are a chemical control system within an organism (plants and animals). Their function is to control the physiological activities within the body, maintaining its proper operation.

In humans, glands (such as the endocrine glands) secrete hormones to regulate cellular activities, and control the health and operation of various organs in the body.
Hormones are like messengers in your body that give orders to your cells to do particular things. They are chemicals that are manufactured by glands and released into the bloodstream, sort of holding a sign up with a type of cell's name on it (like a limo driver at the airport waiting to pick up a client.) Most cells ignore the hormone, but when it comes across the right one its chemical "message" is read and the cell starts to do what it has been told. This message could be a lot of different things, but generally it is meant to keep the body functioning and in balance.

Here are some things that hormones do for the body. Remember, though, they are only the "messengers" that start the cells into action. They go out into the body when told to by a higher power (the gland) and it's the cell that actually does the work.

• make people grow or stop growing,
• make people feel happy or sad,
• speed up or slow down the metabolism,
• starting puberty,
• regulating your fighting, mating, and fleeing instincts.

or it controls and regulates the activites of other organs

In girls with normal reproductive anatomy who have not started their period but who have begun to show signs of puberty--such as breast development and the growth of pubic hair--a progestin challenge generally is the next step in determining the cause of not ever having gotten a period. This test is also used in girls or women whose periods have ceased.

Although it might seem like the point of the progestin challenge is simply to bring on a period, it is considered to be a diagnostic test. Whether a period occurs or doesn't occur after taking the medicine provides information about the patient's current hormonal state that the doctor can then use to determine if further tests are needed.

What's involved in a progestin challenge?

In the progestin challenge test (also called a Provera challenge), a pill form of the hormone progesterone is taken by mouth once a day for five or more days to see if it triggers menstruation. If the period is going to come, it usually starts a few days after the medication is finished, although it can in fact start anywhere from a few days before the prescribed course of pills is finished to as much as two weeks after the last dose is taken.

If there is any possibility that the woman to be tested is pregnant, a pregnancy test should be done before starting the progestin challenge.

Side effects of the progestin medication

Progestins are forms of progesterone, the hormone a woman's body usually makes each month from the time of ovulation until the menstrual period. Most people who take a short course of progestin feel fine, but some have PMS-like side effects, including water retention, breast soreness, irritability, or even depression. These symptoms always resolve as soon as the drug leaves the body--typically a day or two after the medication is finished.

What do the results of the progestin challenge mean?

If a period does occur as a result of taking progestin, it means that the uterus and vagina are properly "connected" and that the uterus has been primed by the hormone estrogen. We know this because exposure to estrogen is required to build up the uterine lining before progesterone can cause the lining to be shed during menstruation.

Once it's been established that estrogen is present, it means that the ovaries contain eggs and are capable of ovulating, but they are currently not "cycling" properly. This condition is called chronic anovulation.

If no period takes place after the progestin challenge and the anatomy of the reproductive tract is normal, it means that the woman has an inadequate level of estrogen, and further tests are needed to sort out the hormonal cause for the lack of periods.