Introduction to endocrinology Flashcards
what is the endocrine system?
Endocrinology is the study of hormonal systems
What is a hormone
A hormone is a chemical messenger that is secreted by certain cells in the body that effects the function of other distant cells in the body
It is secreted in the blood
What are the locations of glands and tissues
and what are their chemical classes
Testis - steroid peptide
Ovaries - steroid peptide
Pancreas - peptide
Adrenal glands
Thyroid glands - iodinated amine peptides
Parathyroid glands - peptide
Pituitary gland - peptides
Pineal gland - amine
what are classifications of hormones and give examples
- Water soluble hormones
○ Peptides
○ Proteins and glycoproteins
○ Catecholamines- Fat soluble hormones
○ Steroids
Thyroid hormones
- Fat soluble hormones
What is the action of hormones through receptors
○ Hormones modulate cellular responses on different cells through specific receptors.
○ Hormone receptors have high affinity for their specific hormone and receptor number can influence a tissue’s sensitivity.
○ Acting through their specific receptors, a hormone can inhibit or stimulate a physiological response.
The availability of the hormone to bind to its receptors can also affect the physiological response (e.g. secretion rate, rate of metabolism or bound serum proteins).
secretion of hormones and how does that differ during the day and night
-high levels of cortisol in the morning - decreases during the day and melatonin increases
what does receptors do when exposed to high continuous levels of hormones
downregulate
what are the roles of endocrine system?
○ Alongside the nervous system, the endocrine system is a major control system in humans
§ Effective cell-cell communication
§ Homeostasis – Monitoring internal environment and makes adaptive changes
§ Regulates growth, development, reproduction, senescence
Responds to and adapt to changes in external environment (e.g., food intake, water availability, temperature change, “stressors” etc)
What is hormone secretion regulated by?
○ Physiological changes
§ Blood glucose levels stimulate release of insulin or glucagon
§ Blood calcium levels regulate parathyroid hormone release
§ Stress causes adrenaline to be released from adrenal medulla
○ Biological endogenous rhythms
§ Monthly luteinising hormone surge prior to ovulation
§ Melatonin released to control daily sleep-wake cycle
§ Gonadotropin-releasing hormone pulses every 90-120 minutes
○ Feedback mechanisms (positive or negative)
Suckling leads to release of oxytocin and prolactin
What is dysregulation of hormone secretion caused by?
○ Changes in the production of hormone through destruction of the endocrine gland, over- or under- production of hormone, surgical removal.
○ Genetic mutation or inappropriate activation of hormone receptors
○ Dietary deficiencies (e.g. iodine, vitamin D)
○ Cancer and other conditions, including tuberculosis
○ Unknown causes
When hormone secretion is dysregulated, dramatic effects on our health are observed
what is the role and where is pituitary gland and hypothalamus
Pituitary gland and hypothalamus
The pituitary gland is one the most important ductless gland which lies at the base of the brain.
It releases number of different hormones into the blood.
It is controlled by the hypothalamus just above it.
The hypothalamus is a cluster of neurons, it links with the posterior and anterior pituitary to control hormone release.
The pituitary gland is one route through which the hypothalamus affects the rest of the body.
Hormones of the anterior pituitary
Adrencorticotrophin (ACTH)
Growth hormone (GH)
Prolactin (PRL)
Leutenizing hormone (LH)
Follicle stimulating hormone (FSH)
Thyroid stimulating hormone (TSH)
