What is a Hormone?

It is a chemical compound released in the human body that helps in regulating and controlling the activities of specific cells or organs. All glands secrete different types of hormones which simulates different regulations. We are going to talk about a specific hormone, Prolactin. This is created by the Anterior Pituitary gland. Moreover, this produces various types of hormones that affect the development and growth of the body’s metabolism, reproduction, and sexuality simulation. So Is Prolactin A Tropic Hormone?

Usually, hormonal communications rely on the production and release of hormones from various glands, like the endocrine gland in the endocrine system. The endocrine function is to release hormones that are absorbed by the endocrine tissue. Then they either directly stimulate target cells or the target cells are hit with another hormone produced by a pituitary gland.

This direct or indirect method of the hormones is called Tropic or non-Tropic hormones, respectively. which involves the Hypothalamus, Anterior pituitary glands, adrenal cortex, etc.

Is Prolactin A Tropic Hormone: adrenal medulla and median eminence
Is Prolactin A Tropic Hormone

The Anterior Pituitary Gland:

This gland is the size of a bean that hangs by a stalk from the hypothalamus, in the brain. It is referred to as the ‘Master Gland‘.

Since its power affects a human body’s metabolism, reproduction, sexuality, growth, and development. This anterior pituitary gland relies on the regulatory hormones, secreted by the hypothalamus, that tell the Anterior Pituitary gland when it should secrete its hormones.

The Anterior pituitary gland produces six different hormones

  1. growth hormone (GH),

2. prolactin,

3. follicle-stimulating hormone (FSH),

4. thyroid-stimulating hormone (TSH),

5. luteinizing hormone (LH), and

6. adrenocorticotropic hormone (ACTH).

Tropic hormones and Non-Tropic hormones:

Tropic hormones are those that trigger or act on other endocrine glands, simulating the production of hormones from those glands. Whereas, Non-Tropic hormones are the ones that directly simulate the target cells or tissues to produce hormones.

An example of a non-tropic hormone is Cortisol which is involved with the stress response. And an example of a tropic hormone is the Adrenocorticotropin hormone that simulates the Adrenal glands. Both Tropic and Non-tropic hormones are needed for the glands to work properly.

The Cortisol hormones released which are a non-tropic hormone in the Adrenal gland cannot be released into the bloodstream without the Adrenocorticotropin hormone being released to simulate the Adrenal gland.

Similarly, the Prolactin hormone is a tropic hormone that is released from the pituitary gland to regulate, initiate and maintain the secretion of milk from the mammary glands.

chemical nature of cortisol and protein synthesis
Is Prolactin A Tropic Hormone

Tropic hormones VS Tropin hormones:

We know Tropic hormones are ones that have an effect on the activities of other endocrine glands and go hand in hand with non-tropic hormones. Let us take an example, Mammotropin is a tropic hormone, whereas Vasopressin is non-tropic.

Tropic should not be confused with Trophic. Trophic hormones stimulate specific body growth effects like hyperplastic. It refers to an increase in the number of cells in a tissue or target organs, which are not cancer cells but can turn into one.  Hypertrophic-exhibits the enlargement of a part of the body or an organ. This is caused due to the increase in the constituent cells.

Whereas, Tropin hormones affect the growth and development of glands directly. Basically, the hormones that end with -tropin are classified as tropic hormones that have tropic effects.

Tropic hormones:

These are the class hormones that are released from the anterior pituitary gland known as the anterior pituitary hormones, which affect the section of other endocrine glands. These anterior pituitary hormones include thyroid-stimulating hormones, follicle-stimulating hormone, corticotropin-releasing hormone (ACTH), luteinizing hormone, growth hormone, etc.

Insulin like growth factors stimulate production
Is Prolactin A Tropic Hormone

Growth Hormone Releasing Hormone (GH):

This is a hormone that is governed and produced by the pituitary gland situated in the posterior lobe of the brain which is related to height, muscle growth, and bone length. The growth hormone levels increase gradually during childhood and it is at their peak during puberty.

During childhood and puberty, the GH stimulates growth in bones and cartilage. For the rest of life, the GH helps in the stimulation of muscles, fat, tissue, and bone.

The synthetic growth hormone, prescribed to children with impaired hormone levels. People tend to abuse these by selling them to bodybuilders, athletes, etc. This abuse can cause an irreversible condition, acromegaly, overgrowth of bones.

Growth hormone gh is very important for smooth muscle
Is Prolactin A Tropic Hormone

Thyroid-stimulating hormone (TSH):

Thyroid-stimulating hormone (TSH) also known as Thyrotropic hormone or Thyrotropin or thyroid hormone is one of the anterior pituitary tropic hormones released from the pituitary gland. It stimulates the thyroid gland and the endocrine glands.

This hormone stimulates the thyroid hormones, Thyroxine(t4) continued by Triiodothyronine(T3) which stimulates metabolism for almost all the tissues in the body. It is also noticed that the TSH concentrations in children are normally higher than in adults.

How is it secreted and its function:

The Endocrine Function of the thyroid gland is regulated by the Anterior Pituitary gland which produces a glycoprotein hormone that is produced by the Thyrotrope cells. The hypothalamus situated in the brain produces thyrotropin-releasing hormone which then stimulates the Anterior Pituitary gland to release TSH.

Like most tropic hormones, Thyroid-stimulating hormone is secreted throughout life but reaches high levels during growth and development, and in response to stress.

TSH is the hormone that stimulates the thyroid gland to secrete the T4 hormone which is then turned into T3, the active hormone that stimulates metabolism.

systemic circulation and blood pressure
Is Prolactin A Tropic Hormone

Adrenocorticotropic hormone (ACTH) or Corticotropin:

Adrenocorticotropic hormone (ACTH) is a hormone that stimulates the release or production of Cortisol, the steroid that is created by the adrenal glands. ACTH is important in the regulation of protein, glucose, and lipid metabolism.

As we all know the production of ACTH is from the pituitary gland, which is part of the endocrine system related to the endocrine gland. Which is the whole network of glands that release hormones that act on target organs, tissues, and sometimes other glands.

Adrenocorticotropic hormone levels increase when Cortisol is low and decrease when the Cortisol is high. When the blood cortisol level decreases the hypothalamus release Corticotropin-releasing hormone(CRH), which produces the ACTH by the anterior pituitary gland which in turn stimulate the production of Cortisol by adrenal glands.

Prolactin:

Yes, Prolactin is a Tropic hormone. Tropic hormones have other endocrine glands as their target and as Prolactin is created and released by the pituitary gland, a hormone that causes milk production in the mammary gland and breast growth during pregnancy. Prolactin secretion level is usually high for pregnant women, and new mothers.

Prolactin is a protein hormone, which was named after its ability to induce lactation in response to the sucking action of young mammals. the prolactin hormone is not only related to the pituitary gland, it is also synthesized within the nervous system, the uterus, the immune system, and other issues associated with conception, including the mammary gland.

Functions of Prolactin:

As we already know it helps in the maintenance and initialization of lactation.

  1. It induces lobular-alveolar and ductal growth systems. 
  2. Moreover, it binds to specific receptors in the gonads, liver, and lymphoid cells. 
  3. It takes part in the synthesis of milk proteins like lactoalbumin and casein. It is also important to control the osmolality. 
  4. This hormone takes part in steroidogenesis, in the formation of steroids from the ovaries, testes, and adrenal cortex. 
  5. Helps in the development of fetal lungs and in the metabolism of subcutaneous fats, carbohydrates, vitamin D, and calcium.

For lactation, the pituitary gland secretes prolactin which is released to the target tissue. That travels to the breasts where the mammary gland starts its simulation and the lactation begins.

Prolactin levels in pregnant women, men, and non-pregnant women:

The level of prolactin is high in pregnant women or nursing women, the levels increase every time the baby-nurses which increases the milk production. This hormone stimulates functions such as growth, metabolism, reproduction, etc.

Normally, both men and women have small amounts of prolactin in their blood. It helps in regulating the menstrual cycle in non-pregnant women and affects sperm production in men.

When the level of Prolactin is high in men or non-pregnant women called hyperprolactinemia which can be a sign of a tumor. The tumor is called Prolactinoma, which is the most common type of tumor caused by the anterior pituitary gland.

In men, the high level can cause galactorrhea. It can reduce the desire for sex, cause the inability to have an erection during sex. However, this can be rectified by using sex steroids that secrete hormones.

And in non-pregnant women, it can also cause galactorrhea-breasts to start producing milk outside of pregnancy, or having problems in conceiving. This can lead to irregular periods, sometimes they might have no symptoms.

Gonadotropins or Luteinizing Hormone (LH):

Luteinizing hormone (LH) is a hormone that affects the sex organs in both men and women. It is a very important hormone that plays a role in puberty, fertility, and menstruation, which is known as Gonadotropin. It affects the ovaries in women and the testes in men.

This hormone is produced in the anterior pituitary gland, in the brain. The hypothalamus produces a gonadotropin-releasing hormone which simulates the Anterior pituitary gland.

The level of LH in our blood can detect and indicate the problems that are associated with a variety of health issues concerning reproductivity.

LH is important in women as it is an important part of the menstrual cycle. LH works with FSH to stimulate the ovarian follicle which causes the egg to grow and triggers the production of estrogen.

The function of LH in men is that the hormone binds to target cells in the testes called the Leydig cells. These cells release testosterone- the hormone necessary for the production of sperm cells.

Follicle-Stimulating Hormone (FSH):

FSH is secreted and synthesized by the gonadotropic cells in the Pituitary gland. Also, FSH is a gonadotropin that regulates other hormones that deal with growth, development, the reproductive process of the body, and pubertal maturation.

FSH and LH work together to stimulate the production of hormones in the reproductive system, like the endocrine system. However, they deal with the reproduction process, reproductive organs, etc. Used mainly in sexual stimulation functions.

In both men and women, FSH’s functions in the stimulation of maturation of the sexually reproductive germ cells. But in males, it induces Sertoli cells for the secretion of androgen-binding proteins(ABP’s), for the activation of inhibin B secretion. In females, it initiates follicular growth that affects the granulosa cells. With the collateral rise in inhibin B, later the levels decrease in the late follicular phase, which is important in the ovulatory cycle.

There are practice tests taken, usually, the FSH and the LH tests are done together, to find the cause of infertility. Also, to find out the problems of the ovarian function, the reason for low sperm count, to confirm menopause. Moreover also to find out any problem with the testicles, or the diagnose for early or late puberty in children. Depending on the negative feedback or the non-negative feedback the doctors diagnose the problem.