Endocrinology I
Tuesday, 27 September 2022 10:47
Endocrine system regulates/functions
• Growth
• Maturation
• Reproduction
• Behavior
• Maintains chemical homeostasis
• Plays a role in environment changes
Endocrine + Nervous System = Neuroendocrinology
• Linked - endocrine glands (ductless) respond to neural stimulation (ANS)
Chemical Messengers
Synthesized by endocrine glands (e.g. brain)
1. Neurotransmitters
2. Hormones
a. Directly enter bloodstream
b. Bind to specific receptors on target tissues = alter function
Specificity of hormones
• Graded release of hormone
• Acts specific to receptor on target cell
• [Blood hormone] important
Endocrine system secretion controlled
[Blood borne reagents] Blood borne stimulatory/inhibitory agents Neuronal input
- e.g. ↑ glucose =
Insulin
Endocrine Gland Hormone Secretions
Pituitary Anterior Pituitary Pituitary Posterior Thyroid Parathyroid Adrenal cortex Medulla Testis Ovary
lobe Intermediate lobe lobe
• Luteinizing • Melanocyte • Vasopressin/antidi • Thyroxine • Parathyroid • Cortisol • Adrenalin • Testosterone • Estradiol
hormone stimulating uretic hormone • Triiodothyronin hormone • Aldosterone • Noradrenalin • Estradiol • Progesterone
• Follicle stimulating hormone • Oxytocin e • Dehydroepiandroster • Androstenedione • Androstenedione
hormone • β-endorphin • Calcitonin one • Inhibin • Inhibin
• Prolactin • Androstenedione • Mϋllerian • FSH-releasing
• Growth hormone stimulating hormone peptide
• Adrenocorticotropin • Relaxin
• Thyroid stimulating
hormone
Non Classical Organs Hormone Secretions
Brain (hypothalamus) Corticotropin- releasing hormone(CRH),thyrotropin-releasing hormone,
growth hormone-releasing hormone (GHRH), somatostatin, fibroblast growth factor
Heart Atrial natriuretic peptide
Kidney Erythropoietin; 1,25 - dihydroxyvitamin D
Liver Insulin growth factor
Fibroblasts IGF-I
GIT Cholecystokinin, gastrin, secretin, vasoactive intestinal peptide, enteroglucagon
Platelets Platelet derived growth factors, transforming growth-β
Lymphocytes Interleukins
Various Epidermal growth factor, transforming growth factor-α
Classes of Hormones
1. Peptide and polypeptide hormones - pure protein
2. Thyroid hormones
3. Steroid hormones - fat molecule attached to it
4. Other chemical messengers
a. Chalones - endogenous + mitotic inhibitors
b. Prostaglandins - ubiquitous + affect many physiological processes
Mechanism of Hormone Release
• Negative feedback loop
○ Long negative feedback loop
○ Short negative feedback loop
• Positive feedback loop
○ e.g. oxytocin in breastfeeding
• Hormone to hormone influence
○ e.g. TSH, LH
• Neural influence
○ Neurohypophysis, adrenal medulla, pineal gland has neural innervation
Hormones are synthesized within cells and packaged in vesicles until released.
Except thyroid and steroid hormones.
Roles of Hormones
• Affect cellular synthesis and secretion of other hormones
• Affect metabolic processes
• Affect contraction and relaxation & muscle metabolism
• Control reproductive processes
• Control excretion and reabsorption of inorganic ions
• Animal behavior
New Section 1 Page 1
, Criteria for endocrine gland
Ductless glands with rich blood supply - needs to be in constant communication with body
Removal produces deficiency
Deficiency responds to replacement - e.g. injecting insulin I.e. synthetic replacement
Normal function after transplantation
Hormones effective in minute quantities (picograms)
Hormone release proportional to stimulus -
Hormones act at a distance from gland and are not metabolic substrates for target tissue - hormone mustn’t act on the gland that secretes it
New Section 1 Page 2
Tuesday, 27 September 2022 10:47
Endocrine system regulates/functions
• Growth
• Maturation
• Reproduction
• Behavior
• Maintains chemical homeostasis
• Plays a role in environment changes
Endocrine + Nervous System = Neuroendocrinology
• Linked - endocrine glands (ductless) respond to neural stimulation (ANS)
Chemical Messengers
Synthesized by endocrine glands (e.g. brain)
1. Neurotransmitters
2. Hormones
a. Directly enter bloodstream
b. Bind to specific receptors on target tissues = alter function
Specificity of hormones
• Graded release of hormone
• Acts specific to receptor on target cell
• [Blood hormone] important
Endocrine system secretion controlled
[Blood borne reagents] Blood borne stimulatory/inhibitory agents Neuronal input
- e.g. ↑ glucose =
Insulin
Endocrine Gland Hormone Secretions
Pituitary Anterior Pituitary Pituitary Posterior Thyroid Parathyroid Adrenal cortex Medulla Testis Ovary
lobe Intermediate lobe lobe
• Luteinizing • Melanocyte • Vasopressin/antidi • Thyroxine • Parathyroid • Cortisol • Adrenalin • Testosterone • Estradiol
hormone stimulating uretic hormone • Triiodothyronin hormone • Aldosterone • Noradrenalin • Estradiol • Progesterone
• Follicle stimulating hormone • Oxytocin e • Dehydroepiandroster • Androstenedione • Androstenedione
hormone • β-endorphin • Calcitonin one • Inhibin • Inhibin
• Prolactin • Androstenedione • Mϋllerian • FSH-releasing
• Growth hormone stimulating hormone peptide
• Adrenocorticotropin • Relaxin
• Thyroid stimulating
hormone
Non Classical Organs Hormone Secretions
Brain (hypothalamus) Corticotropin- releasing hormone(CRH),thyrotropin-releasing hormone,
growth hormone-releasing hormone (GHRH), somatostatin, fibroblast growth factor
Heart Atrial natriuretic peptide
Kidney Erythropoietin; 1,25 - dihydroxyvitamin D
Liver Insulin growth factor
Fibroblasts IGF-I
GIT Cholecystokinin, gastrin, secretin, vasoactive intestinal peptide, enteroglucagon
Platelets Platelet derived growth factors, transforming growth-β
Lymphocytes Interleukins
Various Epidermal growth factor, transforming growth factor-α
Classes of Hormones
1. Peptide and polypeptide hormones - pure protein
2. Thyroid hormones
3. Steroid hormones - fat molecule attached to it
4. Other chemical messengers
a. Chalones - endogenous + mitotic inhibitors
b. Prostaglandins - ubiquitous + affect many physiological processes
Mechanism of Hormone Release
• Negative feedback loop
○ Long negative feedback loop
○ Short negative feedback loop
• Positive feedback loop
○ e.g. oxytocin in breastfeeding
• Hormone to hormone influence
○ e.g. TSH, LH
• Neural influence
○ Neurohypophysis, adrenal medulla, pineal gland has neural innervation
Hormones are synthesized within cells and packaged in vesicles until released.
Except thyroid and steroid hormones.
Roles of Hormones
• Affect cellular synthesis and secretion of other hormones
• Affect metabolic processes
• Affect contraction and relaxation & muscle metabolism
• Control reproductive processes
• Control excretion and reabsorption of inorganic ions
• Animal behavior
New Section 1 Page 1
, Criteria for endocrine gland
Ductless glands with rich blood supply - needs to be in constant communication with body
Removal produces deficiency
Deficiency responds to replacement - e.g. injecting insulin I.e. synthetic replacement
Normal function after transplantation
Hormones effective in minute quantities (picograms)
Hormone release proportional to stimulus -
Hormones act at a distance from gland and are not metabolic substrates for target tissue - hormone mustn’t act on the gland that secretes it
New Section 1 Page 2
