Hormones Flashcards
Define autocrine
the cell that produces and releases the hormone is acted on by the hormone
Define paracrine
The cell produces a signal to alter the behavior of nearby cells
Define Endocrine
Hormones that travel via circulatory system to influence cells further away
What does the anterior pituitary originate from
oral ectoderm
What does the posterior pituitary originate from
neuroectoderm
What is the name of the capillary system which hypothalamic hormones are secreted
hypothalamic-hypophyseal portal system
What 5 hormones are synthesized and secreted by the anterior pituitary; what causes the release of these hormones, what inhibits the release
1) Growth hormone (aka, somatotropin); released by hypothalamic growth hormone releasing factor; inhibited by hypothalamic somatostatin
2) Thyroid stimulating hormone; released by hypothalamic thyrotropin releasing factor; inhibited by somatostatin
3) Adrenocorticotropic hormone; released by hypothalamic corticotropin releasing factor
4) Luteinizing hormone; released by gonadotropin releasing hormone
5) Follicle stimulating hormone; released by gonadotropin releasing hormone
What are the three ligands involved in the insulin-like growth factor system
- IGF-1: somatomedin
- IGF2
- insulin
When are HGH levels the highest?
- deep sleep; phase 4
What type of stress increases/decreases HGH secretion
- physical stress; increases
- psychological; decreases due to an increase in glucocorticoid (also reduces bone/collagen formation
What does HGH do?
- increased DNA synthesis and cell multiplication
What hormone is involved in a permissive relationship with HGH
- thyroid hormone is needed for HGH to work
What three things does HGH directly effect
- Adipose tissue; decrease glucose uptake, increases lipolysis, decreases adiposity
- Liver; increases RNA synthesis, protein synthesis, gluconeogenesis, IGF-1
- Muscle; decreased glucose uptake, increased AA uptake, protein synthesis and lean body mass
how does the local production of IGF-1 affect other systems
- bones/heart/lungs; increased AA uptake, protein synthesis, RNA synthesis, DNA synthesis, organ size/fxn
- Chondrocytes; increased AA uptake, protein synthesis, RNA synthesis, DNA synthesis, collagen, chondroitin sulphate, cell #/size, increased linear growth
How do IGF-1 and growth hormone interact in long bones
- GH stimulates proliferation of chondrocyte precursors > expands proliferative chondrocyte pool & the production of IGF-1
- IGF-1 stimulates clonal expansion via auto/paracrine mechansims & therefore promotes chondrocytet hypertrophy
what does hypopituitarism result in
- stunted growth
- ex, height, penis
what is acromegaly, what does it result from
- enlarged extremities
- hyperpituitarism
at how many weeks of gestation does the thyroid appear
3-4 weeks it appears as an epithelial proliferation at the base of the tongue, it then migrates to the base of the neck
when are TRF and TSH secreted in the fetus
- 18-20 weeks gestation
when does thyroxine/triiodothyronine reach clinically significant levels
- T4; 18-20 weeks
- T3; 30 weeks
what is the purpose of fetal thyroid hormones
to protect against brain development abnormalities caused by maternal hypothyroidism
How does T3/T4 form
- iodide and thyroglobulin combine to form DIT and MIT
- DIT + MIT = T3 ; DIT + DIT = T4
What causes goiter; Derbyshire neck
- lack of iodine in diet
- rare
what is the function of thyroid hormones
- RNA synthesis, increased metabolic rate, stimulated o2 uptake and NRG expenditure
