12.01 Pituitary Gland

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Outline

Overview

  1. Location – sella turcica of sphenoid bone
  2. Also known as “hypophysis”
  3. Components
    1. Pituitary gland is an outgrowth of hypothalamus
    2. Infundibulum – “hypophyseal stalk”
      1. Direct connection with hypothalamus and posterior pituitary
    3. Posterior pituitary – “neurohypophysis”
      1. Functions with infundibulum
    4. Anterior pituitary – “adenohypophysis”
      1. Attaches to posterior pituitary gland
      2. Controls majority of endocrine hormones in the body

Nursing Points

General

    1. Posterior pituitary gland
      1. Secretions
        1. ADH & Oxytocin produced in hypothalamus and transported through infundibulum
        2. Stored and secreted from posterior pituitary
      2. Functions
        1. ADH
          1. Antidiuretic hormone
            1. Promotes retention of water in the kidneys
            2. See Renal Fluid & Electrolyte Balance lesson
            3. Clinical Notes:

 

              • Diabetes Insipidus

 

                1. Not enough ADH

 

              • Syndrome of Inappropriate Antidiuretic Hormone

 

              1. Too much ADH
      1. Oxytocin
        1. Stimulates smooth muscle in uterus during labor and delivery
        2. Lactating breast
          1. Sucking – neurohormonal reflex
            1. Releases oxytocin
            2. Result = ejection of milk
  1. Anterior pituitary gland
    1. Types of hormones
      1. Trophic hormones
        1. Control secretion of other endocrine glands
          1. Hypothalamus-hypophyseal portal system (HHP)
            1. Capillaries in hypothalamus
            2. Portal venules in infundibulum
            3. Capillaries in anterior pituitary
      2. Releasing hormones (from hypothalamus)
        1. Made in hypothalamus and enter HHP
        2. Enter Anterior pituitary and stimulate it to secrete trophic hormones
        3. Each RH specific to a trophic hormone
      3. Example:
        1. Somatotrophic Releasing Hormone causes secretion of Somatotrophic Hormone
    2. Secretions
      1. Somatotrophic hormone (STH) or growth hormone (GH)
        1. Stimulates uptake of amino acids into cells (favors protein synthesis)
        2. Prevents wasting of skeletal muscle
        3. “Hyperglycemic agent”
          1. Stimulates glycogenolysis in liver (releases glucose into blood)
          2. Stimulates fat to be used for energy instead of glucose
        4. Stimulates liver to produce and secrete insulin-like growth factor (IGF) which stimulates growth of bone and cartilage
          1. Hypersecretion → giantism
          2. Hyposecretion → pituitary dwarfism
          3. Acromegaly → hypersecretion in adult
            1. Increased size of hands, feet, bones, jaw
      2. Gonadotropins – reproductive hormones
        1. Follicle stimulating hormone (FSH)
          1. Female
            1. Produce eggs
            2. Secrete estrogens
          2. Male
            1. Produce sperm
        2. Luteinizing hormone (LH)
          1. Female
            1. Stimulates late development of ovarian follicle
            2. Induces ovulation
            3. Makes corpus luteum
            4. Stimulates secretion of estrogens and progesterone
          2. Male
            1. Stimulates Leydig cells in testes to secrete testosterone
      3. Adrenocorticotropic hormone (ACTH)
        1. Stimulates growth and maintenance of adrenal cortex gland
        2. Stimulates production and secretion of hormones from adrenal cortex gland
          1. See Adrenal Gland lesson
      4. Thyrotropic Hormone (Thyroid-stimulating hormone) (TSH)
        1. Stimulates maintenance and health of thyroid gland
        2. Stimulates production and secretion of 2/3 of thyroid hormones
          1. T3
          2. T4
        3. See Thyroid Gland lesson
      5. Prolactin
        1. Female – produces milk in lactating breast
        2. Male – affects Leydig cells…makes them more responsive
          1. Enhances testosterone secretion
      6. Prolactin-inhibiting hormone (PIH)
        1. Prevents secretion of prolactin in non-pregnant state in females.

References:

Betts, J.G., et al. (2017). Anatomy and physiology. Houston, TX: OpenStax, Rice University. Retrieved from https://openstax.org/details/books/anatomy-and-physiology?Book%20details

Transcript

In this lesson we are going to take a look at the pituitary gland.

The pituitary gland is a small gland found in an area called the sella turcica. It sits right behind the eyes and right below the hypothalamus. It’s also known as the hypophysis. It’s made up of three main divisions, the infundibulum, the posterior pituitary and the anterior pituitary.

The infundibulum is also known as the hypophyseal stalk, and it’s the connection between the hypothalamus and the pituitary gland. The posterior pituitary is also known as the neurohypophysis and it helps to function with the infundibulum.

The anterior pituitary is also known as the adenohypophysis, and it attaches to the posterior pituitary gland. It controls the majority of endocrine hormones.

With the posterior pituitary gland, the main two hormones that it deals with are oxytocin and antidiuretic hormone. With the antidiuretic hormone, it is the main hormone responsible for promoting the retention of water in the kidneys, does anti mean, diuretic means to diurese or release water. So the purpose of the antidiuretic hormone is to keep water from going out of the body. With conditions like diabetes insipidus, this is not enough of the antidiuretic hormone, and that means that there is going to be way too much water leaving the body. Oppositely there’s another condition called the syndrome of inappropriate antidiuretic hormone or siadh, and that is too much ADH. That means that there is too much water being retained. There are lessons on both of these disease processes so I encourage you to check those out.

Oxytocin is the other hormone secreted by the pituitary gland. Its main purpose is to stimulate the uterine smooth muscle contraction during labor. The other thing and that it does is it stimulates the ejection of milk with lactation. The suckling of causes a release of oxytocin from the pituitary gland, and that results in the ejection of milk from the breast.

Now in the anterior pituitary gland this is also known as the adenohypophysis and there are two main types of hormones that are secreted. The first one are trophic hormones, and they control the secretion of other endocrine glands. This is done by something called the hypothalamus hypophyseal portal system. they’re transported in from the capillaries in the hypothalamus, and the portal venules in the infundibulum, and the capillaries in the anterior pituitary.

The anterior pituitary also secretes releasing hormones that are made in the hypothalamus. They enter the anterior pituitary gland and then they stimulate the secretion of trophic hormones. Each releasing hormone is specific to a trophic hormone

There are several trophic hormones that we’re going to look at so let’s get started.

The first one is called a somatic trophic hormone or sth. It’s also known as a growth hormone GH. What it essentially does is that it stimulates the uptake of amino acids so it really promotes the synthesis of muscle building because of the uptake of amino acids. It also prevents the wasting of skeletal muscle. In the event of hypoglycemia, the somatic trophic hormone will stimulate something called glycogenolysis and that also stimulates fat to be used for energy. In the liver somatic trophic hormone plays on something called the insulin-like growth factor or igf. If there’s excess secretion of the somatic trophic hormone, it leads to gigantism, and decreased secretion of the somatic trophic hormone result in pituitary dwarfism. As a result if there’s excess secretion it can a tribute to a condition called acromegaly.

There’s another trophic hormone called gonadotropins and these are reproductive hormones. The first one is the follicle-stimulating hormone or FSH. In women the FSH helps to produce eggs and secrete estrogen, and then men it helps to produce sperm. The luteinizing hormone, in women, stimulatesLate development of ovarian follicles, induces ovulation, and makes the corpus luteum. The other thing it does is it stimulates secretion of estrogen and progesterone. In men the luteinizing hormone stimulates the secretion of testosterone in the testes via the leydig cells.

There’s four other hormones that we’re going to look at and they are th eAdrenocorticotropic hormone, the thyrotropic hormone, prolactin inhibiting hormone, and prolactin.

Adrenocorticotropic hormone is the hormone that stimulates the adrenal cortex gland. It’s stimulating growth and maintenance of that gland and also stimulates the production and secretion of the hormones in the adrenal gland.

With the thyrotropic hormone it’s also known as thyroid stimulating hormone. It literally stimulates the thyroid gland and stimulates the production and secretion of 2/3 of the hormones found in the thyroid gland, T3, and T4. I encourage you to check up a lesson on the thyroid gland for more information.

Now prolactin and prolactin inhibiting hormone work hand-in-hand with each other and are both produced by the anterior pituitary gland. Prolactin stimulates the production of milk in lactating breasts, and in men and prolactin affect those leydig cells by increasing the responsiveness. It also enhance his testosterone secretion in Men.

Now prolactin inhibiting hormone prevents the secretion of prolactin in non-pregnant females.

Okay so let’s recap.

The pituitary gland is found in the sella turcica and it is divided into an interior and posterior part.

The posterior pituitary gland is called the neurohypophysis and the anterior pituitary gland is called the adenohypophysis.

The posterior pituitary gland secretes ADH and oxytocin, and the anterior pituitary gland secretes those releasing hormone.

There’s lots of hormones involved with pituitary gland in these include oxytocin, ADH, ACTH, STH, gonadotropin, TSH, Prolactin, and prolactin inhibiting hormone.
And that’s it for our lesson on the pituitary gland. Make sure you check out all the resources attached to this lesson. Now, go out and be your best self today, and as always, happy nursing!