Pituitary - Hypothalamic relationships; Anterior lobe
There is vascular connection between anterior lobe and hypothalamus.
Anterior Pituitary lobe receives releasing and inhibiting hormones from Hypothalamus via portal vein system known as hypothalamic hypophyseal portal system.
Communication between hypothalamus and anterior pituitary occurs though releasing hormone and inhibiting hormones produced by hypothalamus and delivered to anterior pituitary via portal network of capillaries.
Hormones of anterior pituitary
1. Human Growth Hormone (HGH)
This is most abundant growth hormone synthesized by anterior pituitary.
Function
1. It stimulate growth and division of most body cells but especially in bones, skeletal muscle.
2. Stimulation of epiphyseal plate lead to long bone growth, stimulation of skeletal muscle and promotes increased muscle mass.
3. Growth Hormone promotes synthesis and secretion of small protein hormone. These growth promoting protein hormones are produced by liver, skeletal muscle, bone and other tissues in response to human growth hormone.
4. It also regulate aspects of metabolism in many organ liver, intestine, and pancreas; stimulate protein synthesis, especially growth and repair; promotes breakdown of fats and increases blood glucose level.
5. Body growth in response to secretion of growth hormone is evident during childhood and adolescence.
Regulation of Secretion
Secretion of growth hormone is regulated chiefly two Hypothalamic hormone;
Growth hormone releasing hormone (GHRH)
Growth hormone inhibiting hormones (GHIH) called somatostatin.
GHRH (growth hormone releasing hormone) is stimulated by low blood levels of growth hormone.
Secretion of growth hormone (GH) is greater at night during sleep and is also stimulate by hypoglycemia, excercise and anxiety.
The daily amount of GH secretion peak in adolescence and the decline with age.
Inhibition of GH secretion occurs by negative feedback mechanism when blood sugar level rise and also when GHRIH (growth hormone release inhibiting hormone) is released by hypothalamus.
GHIH release is triggered by feedback of growth hormone and IGFs (insulin like growth factor).
Raising level of GH feedback to inhibit it own release.
GHIH blocks release of thyroid-stimulating-hormone. GHIH is also inhibit release of gastrointestinal secretion, pancreatic secretion.
Pituitary - Hypothalamic relationships; Anterior lobe
There is vascular connection between anterior lobe and hypothalamus.
Anterior Pituitary lobe receives releasing and inhibiting hormones from Hypothalamus via portal vein system known as hypothalamic hypophyseal portal system.
Communication between hypothalamus and anterior pituitary occurs though releasing hormone and inhibiting hormones produced by hypothalamus and deliverd to anterior pituitary via portal network of capillaries.
Hormones of anterior pituitary
1. Human Growth Hormone (HGH)
This is most abundant growth hormone synthesized by anterior pituitary.
Function
1. It stimulate growth and division of most body cells but especially in bones, skeletal muscle.
2. Stimulation of epiphyseal plate lead to long bone growth, stimulation of skeletal muscle and promotes increased muscle mass.
3. Growth Hormone promotes synthesis and secretion of small protein hormone. These growth promoting protein hormones are produced by liver, skeletal muscle, bone and other tissues in response to human growth hormone.
4. It also regulate aspects of metabolism in many organ liver, intestine, and pancreas; stimulate protein synthesis, especially growth and repair; promotes breakdown of fats and increases blood glucose level.
5. Body growth in response to secretion of growth hormone is evident during childhood and adolescence.
Regulation of Secretion
Secretion of growth hormone is regulated chiefly two Hypothalamic hormone;
Growth hormone releasing hormone (GHRH)
Growth hormone inhibiting hormones (GHIH) called somatostatin.
GHRH (growth hormone releasing hormone) is stimulated by low blood levels of growth hormone.
Secretion of growth hormone (GH) is greater at night during sleep and is also stimulate by hypoglycemia, excercise and anxiety.
The daily amount of GH secretion peak in adolescence and the decline with age.
Inhibition of GH secretion occurs by negative feedback mechanism when blood sugar level rise and also when GHRIH (growth hormone release inhibiting hormone) is released by hypothalamus.
GHIH release is triggered by feedback of growth hormone and IGFs (insulin like growth factor).
Raising level of GH feedback to inhibit it own release.
GHIH blocks release of thyroid-stimulating-hormone. GHIH is also inhibit release of gastrointestinal secretion, pancreatic secretion.
2. Thyroid stimulating hormone (TSH)
This hormone is synthesized by anterior pituitary and it's release is stimulated by thyrotropin releasing hormone (TRH) from Hypothalamus.
Function
It is tropic hormone that stimulate normal development and secretory activity of thyroid gland.
It stimulates growth and activity of thyroid gland, which secret hormones; thyroxine (T4), , tri-iodothyronine (T3).
Regulation of Secretion
Secretion is regulated by negative feedback mechanism.
Rising blood level of thyroid hormone act on both pituitary and hypothalamus to inhibit TSH (thyroid stimulating hormone) secretion.
3. Adrenocorticotropic hormone (ACTH)
Corticotropin releasing hormone (CRH) from Hypothalamus promotes the synthesis and release of ACTH (adrenocorticotropic hormone) by anterior pituitary.
Function
ACTH stimulates adrenal cortex to release corticosteroid hormones, most importantly glucocorticoids that help body to resist stressors.
ACTH plays a central role in body's response to stress.
Regulation of Secretion
ACTH release stimulated by hypothalamic CRH.
ACTH level are highest at morning.
Secretion is also regulated by Negative feed back mechanism.
Raising levels of glucocorticoids feedback and block secretion of CRH and ACTH release.
Other factor that stimulate secretion include hypoglycemia, excercise and stressors of all type such as emotional status and fever.
4. Follicle stimulating hormone (FSH); Gonadotropins
Just before puberty two Gonadotropins (sex hormone) are secreted by anterior pituitary in response to luteinizing hormone releasing hormone (LHRH), also known as gonadotropins releasing hormone (GnRH) produce by hypothalamus.
Gonadotropins regulates function of gonads (Ovaries and Testes).
In both Male and Female
Follicle stimulating hormone (FSH) stimulate production of gametes (sperm or egg).
FSH target organ are overies and testes.
In female
Luteinizing and follicle stimulating hormone (FSH) are involved in secretion of hormone Oestrogen and progesterone during menstrual cycle.
It stimulate ovulation (release of egg).
As level of Oestrogen and progesterone rise, secretion of LH and FSH is inhibits.
In males,
Luteinizing hormone also called interstitial stimulating hormone (ICSH) stimulates interstitial cell of testes to secrete hormone testosterone.
5. Prolactin
Prolactin hormone secreted by lactotrophs of anterior pituitary which is secreted during pregnancy to prepare the breasts for lactation (milk production) after child birth.
The blood level of prolactin is stimulated by prolactin releasing hormone (PRH) released from Hypothalamus.
Function
In female;
To stimulate milk production by breast.
Regulation of Secretion
Prolactin inhibiting hormone PIH) "dopamine" prevent prolactin secretion.
Decrease dopamine secretion leads to increase prolactin release.
Prolactin together with Oestrogen, corticosteroid, insulin and thyroxine, is involved in initiating and maintaining lactation.
Prolactin secretion raised during period of sleep.
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