Hypothalamic-Pit Relationship Flashcards
Posterior Pituitary Gland
Collection of axons whose cell bodies are located int he hypothalamus.
Supraoptic nucleus (SON) and Paraventricular nucleus (PVN)
Secrete ADH (SON) and oxytocin (PVN)
Anterior Pituitary Gland
Collection of endocrine cells
Secrete: ACTH, TSH, FSH, LH, GH, Prolactin
Portal vessels connect it to hypothalamus
Hypothalamic-Hypophysial Portal Vessels
- Hypothalamic hormones can be delivered to the anterior pituitary directly and in high concentrations
- The hypothalamic hormones do not appear in the systemic circulation in high concetration
Endocrine Axes
Primary endocrine disorder= Peripheral endocrine gland
Secondary= pituitary gland
Tertiary= Hypothalamus
Corticotroph
Release ACTH
Thyrotroph
Release TSH
Gonadotroph
FSH and LH
Lactotroph
Prolactin
Acromegaly
Caused by prolonged, excessive secretion of GH in adult life
Excessive growth of soft tissue, cartilage, and bone in the face, hands, and feet
Develops gradually, may not recognize for many years
Sx-Hypertension, mental disturbance, cardiomegaly, organomegaly, hyperglycaemia, prominent lower jaw, increased heel pad and feet
Diagnosis of Acromegaly
GH stims somatomedin C (insulin like GF1) gene transcription and secretion by the liver
GH levels fluctuate throughout the day whereas IGF-1 levels remains constant
Inadequate suppression of serum GH after a glucose load confirms the dx
Increased IGF-1; failure to suppress serum GH following OGTT; pituitary mass seen on brain MRI
Acromegaly Tx
Work to lower GH serum levels or blocking the effects of GH
-Somatostatin analog, GH receptor antagonist
Surgery to remove pituitary gland
GH Pulsatory Manner
Secreted in pulses, each pulse corresponds to a pulse and bursts of hundreds of GH -secretory pulses by the somatotrophs
Integrated amount of GH secreted each day is higher during the pubertal growth than in younger children or in adults
GH Deficiency
Decrease secretion of GHRH (due to hypothalamic dysfunction), and decrease in GH secretion
Failure to gen somatomedins (the effect of GH that are mediated by somatomedins would be impaired)
GH or somatomedin resistance (deficiency of receptors)
GH Excess
Mostly due to a growth hormone-secreting pituitary adenoma
Consequences depend on development stage
Before puberty: Gigantism
After Puberty: increased periosteal bone growth, organ size, extremity size. Coarsening of facial features, insulin resistance, and glucose intolerance
GH Metablic functions
Diabetogenic effect-Increase in blood glucose concentration
- Causes insulin resistance
- Decrease glucose uptake and utilization by target tissues
- Increased lipolysis in adipose tissue
Increased protein synthesis and organ growth
- Increased AA uptake, stim syn of DNA and RNA
- Effect mediated by somatomedins (IGF-1)
Increased linear growth
- Stims syn of DNA and RNA
- Increased metabilism in cartilage-forming cells and chondrocyte proliferation
- Effect mediated by somatomedins (IGF-1)
