Endocrinology Flashcards
what is endocrinology?
the study,biosynthesis, storage, biochemical and physiological study of the function of hormones and the endocrine cells and tissues that secrete them.
where are glands derived from?
epithelial tissues - specialised for secretion
what are the common features of the endocrine and nervous systems?
- both respond to changes in inputs that the body may suffer
- both release signalling molecules via endocytosis
- neurons and endocrine cells can become depolarisation and release signalling molecules.
surface epithelial cells specialise into…
- exocrine (ducal system)
- endocrine (bloodstream)
what are the two types of hormones and give examples.
- water soluble hormones (catecholamines and protein/peptide hormones)
- lipid soluble hormones (steroids and thyroid hormones T3)
mechanisms for cell to cell signalling via hormones:
- Autocrine- hormone acts on same cell that secretes it or adjacent cells of the same type.
- Paracrine - hormone acts on adjacent cells over a short distance and is transported by interstitial fluid.
- Endocrine - hormone acts on distant cells is transported via the bloodstream.
- Neurocrine - hormone signal originates from neurons and after axonal transport into the bloodstream, Is transported to distant target cells.
what are the three factors that determine hormone levels?
- Rate of production
- Rate of delivery
- Rate of degradation
In what cells are parathyroid hormones made?
Principal or Chief cells
True or false
the parathyroid gland is part of the thyroid
False!
PTG sits on the thyroid but is not part of it (separate glands)
what are the effects of PTH on plasma levels of calcium and phosphate?
increases calcium levels
decreases phosphate levels
what 3 organs does the PTH target and what are the effects?
- Bone - stimulation of osteoclasts (increased bone calcium)
- kidney - stimulation of calcium reabsorption and phosphate loss
- Intestine - increases calcitrol levels leading to increased calcium and phosphate reabsorption from the gut.
what are Osteoclasts and Osteoblasts?
- Osteoclasts- activated/stimulated by PTH to release calcium
- Osteoblasts- lays down calcium and phosphate onto bone to build it up (repair)
what are the processes of fast and slow exchange of calcium between the bone and the plasma?
- Fast exchange - calcium is moved from the labile pool in the bone fluid into the plasma by PTH activated calcium pumps located in the osteocytic-osteoblastic bone membrane.
- Slow exchange - calcium is moved from the stable pool in the mineralised bone into plasma by means of PTH induced dissolution of the bone.
what is Calcitonin and where is is produced?
it is a peptide hormone produced in the parafollicular cells of the thyroid gland.
where is the pituitary gland located?
Sits beneath the hypothalamus in a socket of bone called the Sella Turica.
the pituitary gland consists of what two parts?
- Anterior pituitary
- posterior pituitary
How are the pituitary and hypothalamus connected?
the hypothalamus drops down through the infundibulum to for the posterior pituitary.
what are the hormones released by the Anterior Pituitary?
- Thyroid stimulating hormone (TSH)
- Growth Hormone (GH)
- adrenocorticotropic hormone (ACTH)
- Leutinising Hormone (LH)
- Follicle Stimulating Hormone (FSH)
- Prolactin (PRL)
what is the Hormonal regulation of Growth Hormone secretion?
- GHRH increases GH secretion
- Somatostation decreases GH secretion
How do glucose and free fatty acids regulate GH?
- decreases glucose or fatty acids increase GH
- fasting increases GH
- obesity decreases GH
describe the long loop negative feedback of GH secretion.
Mediated by IGFs
- inhibit release of GHRH
- inhibit action of GHRH in Anterior pituitary
- stimulate release of Somatostatin
Describe the short loop negative feedback of GH secretion
- mediated by GH itself via stimulation of Somatostatin release.
what causes Acromegaly and Gigantism?
growth hormone excess
what causes dwarfism?
Growth hormone deficiency
True or false
IGFs can be Autocrine, Paracrine and Endocrine.
True
What are the two lobes of the thyroid gland joined by?
Isthmus (bow tie shaped)
what is colloid?
extracellular deposits of thyroglobulin present within follicles of the thyroid tissue.
what are the sources of iodine?
dietary only (meats, veg, dairy products, iodised salt)
what are the uses of iodine in the body?
to make thyroid hormone ONLY!
what are the roles of Tyrosine peroxidase in th e production of thyroid?
- Catalyses the additional oh hydrogen peroxide to iodide to convert it to iodine.
- iodination of Tyrosine to DIT
- conjugation of two DIT molecules to thyroxine.
True or false
T4 is more active than T3
false! the other way round
True or false
T4 can be converted into T3
True 🙂
what is TSH?
thyroid stimulating hormone
made up of 2 non covalently bound subunits (alpha and beta).
what are the roles played by TSH in the thyroid?
1) increases thyroglobulin iodination
2) increases DIT/MIT conjugation
3) promotes TG endocytosis
4) increases TG proteolysis
5) stimulates T3/T4 secretion
what biological responses do thyroid hormones affect in the body?
- effects on cellular differentiation and development
* effects on metabolic pathways
what are the general actions of thyroid hormones?
- increase basal metabolic rate and heat production
- stimulation of metabolic pathways
- sympathomimetic effects
what does the term sympathomimetic effects mean?
increase in target cells response to catecholamines by increasing the receptor number on target cells.
diseases related to thyroid dysfunction
* Goitre: an enlarged thyroid gland Hypothyroidism: - in infants - cretinism - in adults - myxedema * Hashimoto's disease Hyperthyroidism - Grave's disease
