Endocrinology: Flashcards
Define hormones:
Hormones: are the natural secretions of endocrine glands
= A hormone is a chemical substance produced in one part of the body (restricted area) that diffuses or transported to another area (circulating hormones), where it influences activity and tends to integrate component parts of the organ. Definition is extended to “local hormones” (any hormones acting in aparacrine,
autocrine, and/or intracrine i.e.
inside acell manner).
Role of hormones are:
Role: integration and control body functions in close co-operation with nervous system.
How are hormones released:
- An action potential in a neuron innervating an endoctine cell, stimulates secretion of a stimulatory neurotransmitter.
- The endocrine cell secretes its hormones into the blood where it will be transported to its target
- An action potential in the neuron stimulates secretion of an inhibitory neurotranmitter
- Then endoctine cell is inhibited and stops producing the hormone
Chemical classes of hormones:
- Amine, peptide, protein, glycoprotein
(hypothalamus, adeno-, neurohypophysis, thyroid, parathyroid, islets of Langerhans) - Steroids
(e. g. gonadal and adrenocortical hormones) - Unsaturated fatty acids
(prostaglandins – local h.)
Hormone-Receptors and their localisation
- what are the receptors made of?
- Where are they localised?
- All known hormone receptors are proteins.
- They may be localised:
- Membrane-active hormones
*on the surface of the cells
(peptide and releasing hormones)
- Gene-active hormones
* in the cytoplasm (steroids)
* on the cell nuclear chromatin (thyroid hormones)
Mode of application:
PO (steroid yes, peptide not)
Size of dose
- What happens if high dose is given?
- what happens if low dose is given?
- Physiological level?
opposite effect:
low oestrogen dose: milk production increases
large dose: milk production decrease
Physiological level: substitution therapy, well tolerated
Side effects of hormones:
- Over dose, permanent large doses: increase number and intensity of side effects
- Corticosteroides - iatrogenic Cushing-disease, obesitas
- oestrogen, progestogens – pyometra,
- insulin – hypoglycaemia
Overlapping effect of hormones found in:
- gluco – mineralo-corticoids
- oxytocin-vasopressin
- FSH – LH
- eCG/PMSG – hCG
For increased hormone efficacy (augmentation) you can use:
- Synthetic analogues (glucocorticoids progesterone, etc.)
- Esterification (steroids)
- complex formation (e.g. insulin zinc complex)
- Enhanced synthesis (sulfonylurea type p.o. antidiabetics)
To decrease hormone efficacy, you can use:
- Antagonists (spironolacton, cabergolin)
- Anti-hormone (antibody against peptides)
- Inhibitors of hormone synthesis (thiouracil-T4, T3)
Which groups of hormones can be found in the body?
- Releasing and inhilbitory hormones
- Hormones in the pituitary gland
- Hormones of the thyroid gland
- Hormones of the endrocrine pancreas
- Sex steroid hormones and anabolic agents
- Corticosteroids
- Hormones of the pineal gland
Releasing and inhilbitory hormones:
Which hormones are most important?
- Gonadotrophin-releasing hormone (GnRH) Anterior Pituitary (AP) ---> releases LH and FSH ---> ovary, testis
- Corticotrophin-releasing hormone (CRH)
AP —> releases ACTH —-> adrenal cortex —>
Diagnostic agent to asses ACTH secretory capacity 1 µg/kg iv. - Thyrotrophin-releasing hormone (TRH)
- Somatotrophin-releasing hormone (GRH)
- Somatotrophin-inhibitory hormone (GIH)
- Prolactin-releasing hormone (PRH)
- Prolactin-inhibitory hormone (PIH)
Releasing and inhilbitory hormones:
- production site and transport
Produced by hypothalamus and transported via the hypophyseal portal system into the adenohypophysis.
Hormones in the pituitary gland
- production site?
Adenohypophysis (anterior pituitary - oral ectoderm)
Neurohypophysis (posterior pituitary - neural ectoderm)
Hormones in the pituitary gland
- which hormones are produced in adenohypophysis?
- Somatotrophin
- Adrenocorticotropic hormone (corticotrophin, ACTH)
- Thyrotrophic hormone (TSH, thyrotropin)
- Prolactin (lactotrophin)
- Gonadotrophins
- Follicle-stimulating hormone (FSH)
- Luteinizing hormone (LH)
- (Non-hypophyseal gonadotrophins)
- Human chorionic gonadotrophin (hCG)
- Pregnant mare’s serum gonadotrophin (PMSG, eCG)
mainly FSH-like activity, but LH-like activity is significant
HORMONES OF THE PITUITARY GLAND
Hormones produced in neurohypophysis are?
- Antidiuretic hormone (ADH, vasopressin)
renal tubules - Oxytocin
uterine myometrium and mammary myoepithelium
SEX STEROID HORMONES and ANABOLIC AGENTS
- What are they?
- which exists?
= Endogenous steroids and synthetic compounds with steroid activity
- Oestrogens
- Progesteron and progestagens
- Androgens
CORTICOSTEROIDS
- which types?
Mineralocorticoids
Glucocorticoids
hormones of the pineal gland:
- Melatonin (sc. implant 18 mg preseason mating in ewe, doe, goat)
Somatotropin:
- what kid of substance is it?
- How to give it?
- growth hormone/ insulin-like growth factor production in liver
- orally it is ineffective
Somatotropin:
- release is controlled by:
- Release of GH is controlled by Growth Hormone Releasing Hormone and Growth Hormone-inhibitori Hormone
- Ghrelin: primarily from GI and hypothalamus (+kidney, placenta, pituitary gland)
- Plansma levels of GH