Hypothalamus and Pituitary Gland Hormones
Hypothalamus and Pituitary Gland
- The most commonly used sample is serum.
- In some cases, 24 hours urine sample is collected.
Indications for Hypothalamus and Pituitary glands hormones
- These hormones are estimated for:
- Diagnostic purposes.
- For a therapeutic reason.
- To evaluate ovulation.
- To evaluate spermatogenesis.
- To treat endometriosis and uterine fibroids.
- To evaluate precocious puberty.
- To treat prostatic carcinoma.
- To find GH deficiency.
Pathophysiology of Hypothalamus and Pituitary glands
- Hormones communicate between cells and depend upon neuronal and endocrine signals to regulate body functions.
- Hormones are chemical substances that are formed in various glands.
- These hormones stimulate or inhibit the growth or function of other tissues and organs.
The pituitary gland hormones functions:
- Hypophysis regulates the endocrine system. This is called the master endocrine organ.
- It takes place by integrating signals from the brain with the feedback from the concentration of the hormones in the blood, leading to the intermittent release of the hormones from the target endocrine glands.
- These hormones regulate growth, thyroid functions, adrenal gland functions, gonadal functions, and water and salt homeostasis.
- Vasopressin is known as an antidiuretic hormone (ADH), and oxytocin is produced in the hypothalamus and stored in the posterior pituitary lobes.
- So posterior pituitary gland (neurohypophysis) is not a gland but a storage site for ADH and oxytocin.
The hypothalamus gland:
- The neurons that give rise to hypophysiotropic hormones are themselves influenced by the hypothalamic neurotransmitters:
- These neurotransmitters modify the secretory activity of the anterior pituitary gland.
- Cytokines also modify this neuroendocrine axis.
- The hypothalamic-pituitary-adrenal axis is modified by interleukin 1 (IL-1) and interleukin 6 (IL-6), produced due to infection or stress.
- Corticotropin-Releasing Hormone (CRH).
- This hormone will stimulate the production and secretion of ACTH by the anterior pituitary glands.
- Thyrotropin Releasing Hormone (TRH).
- This hormone stimulates the anterior pituitary glands’ production and secretion of TSH and prolactin.
- Gonadotropin-Releasing Hormone (GRH).
- This hormone stimulates the anterior pituitary gland’s production and secretion of FSH and LH.
- Growth hormone-releasing hormone (GRH).
- This hormone stimulates the anterior pituitary gland’s production and secretion of GH.
- Growth hormone inhibiting hormone (GIH).
- This hormone inhibits the anterior pituitary gland’s production and secretion of GH and TSH.
- Prolactin inhibiting factor (PIF).
- This is considered the neurotransmitter that inhibits the production and secretion of prolactin, TSH, FSH, LH, and GH by the anterior pituitary gland.
Anterior Pituitary Gland:
- The pituitary gland consists of two lobes:
- The anterior lobe is called adenohypophysis.
- The posterior lobe is called neurohypophysis.
- This gland is present at the base of the skull in a bone cavity called sella turcica.
- The gland is small, measuring 1 cm or less in width/height and weighing 500 mg.
- Most pituitary gland hormones are proteins (consists of peptides) or peptides (short chains).
- The cells of the anterior lobes of the pituitary glands are divided into:
- Acidophilic cells that stain with acidic stains are around 40%.
- Basophilic cells stain with the basic dyes and are around 10%.
- Chromophobic cells do not stain with either acid or basic dyes and are around 50%.
- Immunohistochemistry divides the cells into:
|Type of the cells||Hormone secreted||Stimulant for the secretion|
|Somatotropes||Growth hormone (GH)||
|Thyrotrophs||Thyroid-stimulating hormone (TSH)||
|Gonadotropes||Follicle-stimulating hormone (FSH)||
|Gonadotropes||Luteinizing hormone (LH)||
|Corticotropes||Adrenocorticotropin hormone (ACTH)||
- Secretion of the hormones from the anterior pituitary glands is controlled by the hypothalamus.
- Hypothalamus secretes small peptides that are known as releasing or inhibitory factors.
Inhibitory chemicals for the secretion of hormones:
|Growth hormone (GH)|
|Follicle-stimulating hormone (FSH)||
|Adrenocorticotropin hormone (ACTH)||
|Thyroid-stimulating hormone (TSH)||
Anterior pituitary hormones:
- Adrenocorticotropic hormone (ACTH).
- This hormone stimulates the secretion of cortisol by the adrenal gland.
- Growth Hormone (GH).
- This hormone promotes growth in soft tissue, cartilage, and bone.
- Thyroid stimulation hormone (TSH).
- This hormone stimulates the secretion of the thyroid hormone T3 and T4 by the thyroid gland.
- Prolactin Hormone (PRL).
- This hormone’s main role is in the initiation and maintenance of lactation.
- Prolactin induces ductal growth, the lobular alveolar system, and the synthesis of milk production.
- Follicle-stimulating hormone (FSH).
- This hormone controls the functional activity of gonads.
- In the male, this stimulates spermatogenesis.
- Females stimulate the growth of ovarian follicles in the presence of LH. This promotes the secretion of estrogen by the mature follicle.
- Luteinizing hormone (LH).
- This hormone controls the functional activity of the gonads.
- Males produce testosterone through the Leydig cells of the testes.
- In females, it leads to the release of the ovum from the ovarian follicle, in which FSH ripens.
- It transforms the follicle into a corpus luteum that secretes the progesterone.
Posterior Pituitary Gland hormones:
1. Antidiuretic Hormone (ADH).
- This maintains water homeostasis.
- It increases water reabsorption by the distal tubules and collecting ducts of the kidneys, increasing urine concentration.
- This also leads to vasoconstriction to increase blood pressure.
- This will stimulate uterine contraction during labor.
- This may be used to induce labor.
- It helps in the breast for milk release from the mammary ducts.
Question 1: What are the hormones of the posterior pituitary gland.
These are ADH and Oxytocin.
Question 2: What is the inhibitor of prolactin.
Prolactin is inhibited by dopamine, serotonin, and endorphins.