Pituitary gland Flashcards
what makes up the hypothalmic pituitary axis?
- the hypothalamus and pituitary gland form complex unit that serves as the major link between endocrine and nervous system.
describe the location of the pituitary gland.
what does it modulate alongside the hypothalamus?
- beneath the hypothalamus in socket of bone called ‘sella turcica’.
- body growth, reproduction, lactation, adrenal gland function, puberty, thyroid function, water homeostasis.
describe the neurocrine functions of the posterior pituitary.
- physically connected to the hypothalamus (as it drops through the infundibulum).
- oxytocin (milk let down, uterine contractions) and ADH (regulates body water) from supraoptic and paraventricular nuclei of hypothalamus transported to posterior.
- stored and released from here, DOES NOT SYNTHESISE.
what is the function of the anterior pituitary function?
- hormones synthesised in hypothalamus and transported and stored in median eminence before released to hypophyseal portal system.
- stimulate/ inhibit target endocrine cells in anterior pituitary gland.
- endocrine and paracrine functions.
(anterior can synthesise own hormones).
compare the anterior and posterior pituitary pathways.
- posterior : direct effects on target tissues via oxytocin & ADH.
- anterior : secreted into hypophyseal portal system affecting endocrine cells within anterior pituitary.
name some hormones produced by the hypothalamus and what their significance is?
*directly affects release of anterior pituitary hormones.
*TROPIC (NOT TROPHIC that affect growth) are hormone that affect release of other hormones.
- TRH, PRH, GnRH, GHRH etc.
LOOK OVER SLIDES.
name the 6 hormones produced by the anterior pituitary and their function.
- TSH : secretion of thyroid hormone from thyroid.
- ACTH : adrenal cortex hormone secretion.
- LH : ovulation and sex hormone secretion.
- FSH : development of eggs and sperm.
- PRL : mammary gland development and milk secretion.
- GH : growth and energy metabolism.
describe negative feedback and the hypothalamus + pituitary + adrenal axis.
- high cortisol negatively feedbacks onto hypothalamus to inhibit release of CRH and anterior pituitary to inhibit ACTH.
describe the meaning of the following terms.
- cell necrosis, apoptosis, hypertrophy, hyperplasia, atrophy.
- necrosis : cell death by damage.
- apoptosis : programmed cell death.
- hypertrophy : increase in cell size like exercise.
- hyperplasia : increase in cell number.
- atrophy : decrease in cell number or size.
describe the structure of the growth hormone.
- produced in anterior pituitary stimulated by GRH and inhibited by somatostatin.
- peptide hormone made from cleaved signal peptide.
- indirect growth promoting effects via insulin-like growth factors (somatomedins).
- in response to GH liver and skeletal muscle produce and secrete IGF.
what is the function of growth hormone?
- essential for normal growth during childhood and teens.
- stimulates long bone growth via length and width prior to epiphyseal plate close and width after.
- IGF stimulates both bone and cartilage growth.
adults : GH, IGF help maintain muscle and bone mass and promote healing and tissue repair and modulate metabolism and body composition.
how is GH secretion controlled?
- via hypothalamus and CNS control GHRH to increase, Somatostatin to decrease.
- GH increases in deep sleep and decreases in rem.
- stress, exercise increases GH.
- low glucose or FA increases, high decreases.
- fasting increases and obesity decreases.
- long loop negative : via IGF in hypo, inhibits GHRH, stimulates somatostatin so GH inhibited from ant.pit.
- short loop negative : by GH itself via somatostatin release.
what happen in deficiency or excess of GH?
- pituitary dwarfism in deficiency : height below 3rd percentile, slower rate, delayed or no sexual development –> GH therapy.
- gigantism in excess : in childhood pituitary adenoma often cause. in adults after epi.plate stops growing acromegaly, large extremities like hands, lower jaw, feet.
how does GH work at cellular level?
- activated janus kinases (JAKS) which activate signalling pathways.
- these in turn activates transcription factors and IGF production.
what is the significance of insulin-like growth factors (IGF)?
- 2 IGFs : IGF1 in adults, UGF2 in foetal growth.
- paracrine and endocrine functions.
- acts through IGF receptors to modulate hyperplasia, hypertrophy, protein synthesis rate increase, increase in lipolysis rate in adipose.
