Download - Introduction to endocrinology
Introduction to Endocrinology
Course Plan
1. Introduction2. Pituitary gland, Hypothalamus and their
disorders3. Hypothyroidism4. Hyperthyroidism5. Diabetes Mellitus6. Acute Complications of Diabetes Mellitus7. Chronic Complications of Diabetes Mellitus8. Disorders of the Adrenal Cortex9. Phaeochromocytoma10.Calcium and the Parathyroids
Introduction
• Endocrinology is the understanding of hormone secretion, hormone action, and principles of feedback control.
• The endocrine system is evaluated primarily by measuring hormone concentrations.
• Most disorders of the endocrine system are amenable to effective treatment once the correct diagnosis is determined.
Introduction
• The term endocrine was coined by Starling • Hormones secreted internally (endocrine) • Externally (exocrine) i.e. into a lumen, such as the
gastrointestinal tract. • The term hormone - derived from a Greek phrase meaning
“to set in motion,” aptly describes the dynamic actions of hormones as they elicit cellular responses and regulate physiologic processes through feedback mechanisms.
Introduction
The Endocrine organs
1. Hypothalamus2. Pituitary gland3. Thyroid gland4. Parathyroid glands5. Adrenal glands6. Pancreatic islet cells (Endocrine Pancreas) 7. Gonads8. Others – Eg. The gastrointestinal tract
The classic endocrine
organs
Introduction
Other hormones
Kidney (Erythropoietin, Renin)
Heart (ANP)
Lungs (PG, ACE)
GIT (Many GI hormones)
Placenta (Many hormones during Pregnancy)
Hormones
5 major classes
1. Amino acid derivatives dopamine, catecholamine, and thyroid hormone;
2. Small neuropeptides gonadotropin-releasing hormone (GnRH), thyrotropin-releasing hormone (TRH), somatostatin, and vasopressin;
3. Large proteins insulin, luteinizing hormone (LH), and PTH produced by classic endocrine glands;
4. Steroid hormones such as cortisol and estrogen;5. Vitamin derivatives such as retinoids (vitamin A) and
vitamin D.
Hormones
A variety of peptide growth factors , most of which act locally, share actions with hormones.
• As a rule – protein based hormones act on the ‘cell surface receptors’ and steroid based hormones act on ‘intracellular nuclear proteins’
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(a) Humoral: in response to changing levels of ions or nutrients in the blood
(b) Neural: stimulation by nerves
(c) Hormonal: stimulation received from other hormones
Mechanisms of hormone release
Endocrine glands
Sites of hormone action
Exocrine glands
Autocrine glands
Sites of hormone action
Neurotransmission
Functions
• Maintenance of growth & development – Growth hormone, Thyroxine, insulin, Glucocorticoid, & Gonadal hormones
• Maintenance of internal environment – ADH, Mineralocorticoids, PTH
• Regulation of energy balance and metabolism –Insulin, glucagon , Leptin & Ghrelin
• Reproduction & species propagation – Gonadal & Pituitary hormones
Interactions between
hormones
• When two or more hormones work together to produce particular result their effects are said to be synergistic.
• These effects may be additive or complementary.
• Additive: Same effect of the hormones on one target organ, for example, epinephrine and norepinephrine on heart rate
• Complementary: Work on different stages of a physiological procedure, for example, FSH (initiation) and testosterone (maintenance) on spermatogenesis
1. Synergistic effects
Interactions between
hormones 1. Synergistic effects
Interactions between
hormones
A hormone is said to have a permissive effect on the action of a second hormone when it enhances the responsiveness of a target organ to the second hormone or when it increases the activity of the second hormone.
• Estrogen – Expression of progesterone receptors on uterus – progesterone effect on the uterus.
• Glucocorticoids – effects of catecholamines on cardiovascular system
• Thyroid hormones- effects of catecholamines on cardiovascular system
2. Permissive effect
Interactions between
hormones
In some situations the actions of one hormone antagonize the effects of another.
Lactation during pregnancy is prevented because the high concentration of estrogen in the blood inhibits the action of prolactin and hence milk secretion.
2. Antagonistic effect
Example of an endocrinal axis
Regulation by negative feedback and direct control is shown, along with the equilibrium between active circulating free hormone and bound or metabolized hormone.
Endocrinal axes
Regulation
• Feedback control , both negative and positive, is a fundamental feature of endocrine systems.
• Each of the major hypothalamo-pituitary-hormone axes is governed by negative feedback, a process that maintains hormone levels within a relatively narrow range
Regulation
• As an example, a small reduction of thyroid hormone triggers a rapid increase of TRH and TSH secretion, thyroid gland stimulation and increased thyroid hormone production.
• When thyroid hormone reaches a normal level, it feeds back to suppress TRH and TSH.
• Feedback regulation also occurs for endocrine systems that do not involve the pituitary gland, Eg. glucose inhibition of insulin secretion
Overview of Endocrine disorders
Overview of Endocrine disorders
Presentation
Investigations