Endocrinology Flashcards
What are hormones?
Regulator substance of cellular activity released by endocrine glands and act at sites remote from site of production
Define endocrine, autocrine and paracrine
Endo: act in remote tissues
Auto: act on cell where they are excreted
Para: act on adjacent cells
What are the main hormone functions?
Homeostatic mechanisms in the body
Energy production, utilisation and storage
Growth and development
Reproduction
What are the classification of hormones - give examples
Peptides - ACTH, Prolactin, Insulin
Glycoprotein - LH, FSH and TSH
Steroids - cortisol, testosterone and vit D
Catechol amines - Adrenaline and noradrenaline
Outline the mechanisms of action of hormones
Trigger cellular activity or genetic regulation
1) protons and amines bind cell surface receptor and trigger intracellular secondary messenger systems which propagate throughout a cell (quick - 30s to 2 min)
2) steroids diffuse directly into cells and bind intracellular receptor to form a complex than travels to uncles and affects genes (can take hours but have longer effects)
How are endocrine response modulated ?
Glands are usually organised into hierarchical loops that allow feed forwards and feedback to regulate. Loops can be long or short. Majority are self-limiting so incorporate some form of negative feedback loop.
What are the four major endocrine pathways in biochemistry?
1) hypothalamus - pituitary - adrenal (HPA axis)
2) hypothalamus - pituitary - gonadal axis
3) hypothalamus - pituitary - thyroid axis
4) anti diuretic hormone (ADH) - water balance
Discuss the relationship between the hypothalamus and pituitary gland
Hypothalamus is region of brain involved in wide range of homeostatic and metabolic processes. Acts on anterior pituitary using peptides carried by capillaries. Acts posterior pituitary using neuronal signals
What are the pituitary hormones?
Anterior: adrenocorticotrophic hormone (ACTH), growth hormone, follicle stimulating hormone, luteinising hormone, prolactin and thyroid stimulating hormone
Posterior (water balance) : anitdiuretic hormone, AKA arginine vasopressin and oxytocin
Outline the HPA axis
Stress in deuces release of CRH from hypothalamus, stimulating ACTH from pituitary gland, which in turn stimulates cortisol from adrenal gland. Cortisol stimulates glucose production and modulates the immune system, as well as providing negative feedback to the hypothalamus
Outline the HP gonadal axis for both sexes
Male: Gonadothrophin releasing hormone stimulates LH and FSH from pituitary, in turn stimulate testosterone and spermatogenesis respectively from testes. Testosterone then inhibits Gonadothrophin releasing hormone
Female: Gonadothrophin releasing hormone stimulates LH and FSH from pituitary, in turn stimulate progesterone and estrogen and estrogen respectively form ovaries. Progesterone and estrogen both negative feedback on Gonadothrophin releasing hormone. Estrogen causes ovulation and can have positive and negative feedback on FSH release
Outline the HP thyroid axis
Hypothalamus releases TRH which stimulates TSH release form pituitary gland. TSH stimulates T4 and T3 release from the thyroid gland. T4 cusses additional T3 release from peripheral tissues. T3 inhibits its TSH release and TRH release. T3 and 4 are main regulators of metabolic rate
Outline the ADH - water balance axis
Increased plasma osmolality causes ADH release from the pituitary gland and increased thirst. Increased water inhibit hypothalamus. ADH release, also by decreased blood pressure, stress, pain, nausea and drugs, will increase water reabsorption and decrease urine volume. Decreased urine volume inhibits hypothalamus.
What are the two methods for measurements of hormones in clinical biochem?
Immunoassay: using labelled antibody against specific region present on target. Often feasible if unique epitope exists
Chemical detection: HPLC and mass spec
What are the measurements considerations with hormones?
- similar structures
- correct form of the hormone (bound/unbound). Unbound usually the active form but is hard to measure, instead measure total and minus the bound form?
- correct sample type
- ## on treatment?
