9 calcium metabolism and HPA Flashcards
what are two main examples of ca2+ transporters?
ca2+ - mg2+ ATPase: high affinity, low capacity
na+ - ca2+ exchanger: low affinity, high capacity
What can increase the risk of calcium deficiency ?
lactose free diet
coeliac disease
osteoporosis
breastfeeding
menopausal females
organs involved in calcium deficiency?
Gut
bone
kidneys
bone is made of ? bound to a proteoglycan matrix
calcium hydroxyapatite
Action of PTH on bone?
intermediate action
binds to osteoblasts - inhibits bone formation and release cytokines (chemical messenger)
cytokines stimulate osteoclasts - increase bone resorption/breakdown and release Ca2+ and phosphate.
action of PTH on kidneys?
stimulates reabsorption of filtered Ca2+
increased loss of phosphate in urine
activates calcitriol (from Vit D) - uptake of Ca2+ from gut
how does absorption of Ca2+ occur?
dependent on Vit D (converted by liver/kidney to active form calcitriol)
D3 - from sunlight (7, dehydroxycholesterol)
D3 - from diet (25-hydroxyvitamin )
cells that secrete PTH?
chief cells
PTH initiates what response to low calcium ions?
Mobilization of calcium from bone.
Enhancing absorption of calcium from the small intestine.
Suppression of calcium loss in urine.
What is PTHrp?
a hormone - PTH-related peptide; that acts at PTH receptors.
hypercalcemia causes and symptoms
increase in serum calcium levels
causes- hyperthyroidism, renal failure, drug induced
symptoms - kidney stones, stomach pain, nausea, easy fractures
hypocalcemia causes and symptoms
decrease in serum calcium levels
causes - hypothyroidism, GI malabsorption, renal loss
symptoms - impaired cognition, twitching, seizures
Calcitonin opposes the action of which hormones
Parathyroid
Calcitriol
How does Calcitonin reduce ECF calcium levels
Inhibit osteoclast
Decrease kidney resorption
How is calcium lost from the body
Urine
Faeces
How is intracellular calcium controlled
Pumped out of cells
Sequestered into organelles(Sarcoplasmic reticulum and mitochondria)
How much calcium in extracellular fluid
2.1mmol/l
What are some roles of calcium (4)
Lower blood pressure
Regulate heart rhythm
Importance in intracellular signal pathway
Assists in Normal blood clotting
What are the 3 categories of hypercalcaemia causes
Hormonal
Non hormonal
Drugs
What are the 3 principle cells in the Parathyroid
Chief cells
Oxyphil cells
Adipose cells
What are the causes of hypocalcaemia
Hypoparathyroidism
Hypovitaminosis D
GI malabsorption
what are the CNS effects of hypocalcaemia
irritability
seizures
personality changes
What are the general effects of hypercalcaemia
Stones(kidney stones )
Moans (depression)
Groans(abdominal pain)
What are the hormonal causes of hypercalcaemia
Primary hyperparathyroidism
Hypervitaminosis
What are the main hormone regulators of calcium
Parathyroid
Vitamin D
Calcitonin
what are the neuromuscular effects of hypocalcaemia
tetany
parestesia
twitching
convulsions
What are the non hormonal causes of hypercalcaemia
Renal failure
What calcium is physiologically active
Free ionised calcium
What can be used in managing a deficiency or excess in pituitary hormone secretion
hormonal therapy
medical therapy
What can lead to a calcium imbalance
Poor absorption
Poor calcium intake
Excessive loss-lactation
What does hypervitaminosis D cause
Excessive production of 1,25 dihydroxy vitamin D3
Suppression of PTH
What drugs can cause hypercalcaemia
Thiazides
Lithium
What feedback system in parathyroid hormone
negative
What gland is parathyroid hormone released from
parathyroid gland
What inhibits parathyroid release
High extracellular calcium
What is 25 hydroxy vitamin D3 converted to in the liver
1,25-dihydroxy vitamin D3
What is 7-dehydrocholesterol converted to in the skin
Cholecalciferol
What is calcitonin secreted from
Parafollicular cells of the thyroid gland
What is cholecalciferol converted to in liver
25-hydroxy vitamin D3
what is humoral hypercalcaemia of malignancy
tumour secretion of parathyroid hormone-related peptide [PTHrP]
What is hypercalcaemia
Calcium levels rises
What is hypocalcaemia
Calcium levels fall
What is the action of calcitriol on the bone
Stimulate bone re-modelling
What is the action of Parathyroid on the bone
Bind to osteoblasts
Inhibit bone formation
Release cytokines which stimulate osteoclasts
Increased bone breakdown
Release of calcium and phosphate
What is the action of parathyroid on the kidneys
Stimulate increased reabsorption of calcium
Increased loss of phosphate in urine
Activation of calcitriol
What is the action of parathyroid on the kidneys
Stimulate increased reabsorption of calcium
Increased loss of phosphate in urine
Activation of calcitriol
What is the normal response to hypercalcaemia
Decreased Parathyroid
Decreased calcitriol -less calcium taken up from gut
Less calcium absorption from kidney
Decreased breakdown of bone
Increase bone formation
What is the normal response to hypocalcaemia
Increased parathyroid production
Increased calcitriol
Increased calcium absorption from gut and kidney
Increased breakdown of bone
Decreased bone formation
What is the process for negative feedback control for parathyroid
Decreased calcium stimulate parathyroid
Parathyroid acts on bone and released calcium and raises calcium concentration
Increased calcium inhibits parathyroid release
What is the role of calcitriol in the gut
Increased expression of proteins that import Ca2+
Promote absorption of calcium from diet
What is the role of PTHrP
Cartilage development
Calcium transport in placenta
What is the role of the chief cells
Produce and degrade parathyroid
What occurs as a result of Parathyroid suppression
Decreased bone resorption
Increased urinary loss of calcium
Decreased 1,25-dihydroxy Vitamin D3 production
what organ systems affected by hypocalcaemia
Neuromuscular
CNS
Cardiovascular
What organ systems are effected by hypercalcaemia(5)
CNS
GI
Renal
Skeletal
Cardiovascular
What stimulate the synthesis and secretion of parathyroid
Low extracellular calcium
By what method is PTHrP released
Paracrine
How are lactotropes controlled
Hypothalamus secrete dopamine
dopamine inhibit prolactin secretion
lactotropes release increased due to prolactin reduction
How are neurones that secrete hypothalamic releasing hormones affected
nervous inputs - enviroment influences endocrine system
chemical signals-feedback
how does hypothalamus control anterior pituitary secretion
release neurohormones from median eminence which travels in hypophyseal portal circulation to anterior pituitary gland
How is Gonadotropin Releasing Hormone (GnRH) released
small pulses
how is the hypothalamus and anterior lobe of pituitary gland connected
vascular connection
how is the hypothalamus and posterior lobe of pituitary gland connected
neurological connection
how is the pituitary gland developed
anterior lobe formed from ectodermal cells from roof of pharynx
fusion of anterior lobe with down growth neural tissue from hypothalamus
what are gonadotropes controlled by
Gonadotropin Releasing Hormone (GnRH)
what are somatotropes controlled by
Growth Hormone Releasing Hormone (GHRH)
what are the effects of Adrenocorticotropic hormone deficiency
mild hypotension
hyponatraemia (low level of sodium in blood)
What are the effects of gonadal deficiencies
loss of libido
loss of secondary sexual hairs
erectile dysfunction
What are the effects of Growth hormone deficiency
growth failure in children
impaired wellbeing in adults
What are the effects of hyperparathyroidism
Hypercalcuria
Increased risk of fracture
Increase risk of kidney stones
what are the effects of Thyroid stimulating hormone deficiency
weight gain
dry skin
cold intolerance
What can cause hypoparathyroidism
Post surgery
Autoimmune
Pseudohypoparathyroidism( PTH resistance)
what cell produces adrenocorticotropic hormone
corticotropes
what cells are most abundant in the anterior pituitary
somatotropes
what cells produce thyroid stimulating hormone
thyrotropes
what condition associated with excess Adrenocorticotropic hormone
cushing’s disease
what conditions are associated with excess growth hormone
Acromegaly
gigantism
what controls thyrotropes
Thyrotropin Releasing Hormone (TRH)
what do Follice stimulating hormone and luteinising hormone act on
gonads to control reproduction
what does anterior pituitary arise from
Rathke’s pouch
what does anterior pituitary secreate
tropic hormones
What does Gonadotropin Releasing Hormone (GnRH) stimulate
Luteinising and follice stimulating hormone secretion
what does posterior pituitary arise from
neuroectoderm
what does prolactin do
controls milk production and reproductive processes
what is follice stimulating hormone produced by
gonadotropes
what is growth hormone produced by
somatotropes
What is hypopituitarism
decreased secretion of one or more pituitary hormones
what is luteinising hormone produced by
gonadotropes
what is prolactin produced by
lactotropes
What is pseudohypoparathyroidism
Parathyroid resistance
what is pituitary adenomas
growth or tumor on the pituitary
excess hormonal secretion
what is the management for pituitary tumours
Surgery
radiotherapy
medical therapy
what is the most common cause of pituitary disease
pituitary adenomas
what is the role of the infundibulum
connection between the hypothalamus and the posterior pituitary.
What type of gland is anterior pituitary
endocrine
what type of gland is posterior pituitary
neurosecretory gland
Where is the parathyroid gland located
4 glands around the thyroid gland
4 glands around the thyroid gland
base of brain in sella turcica
Why does parathyroid increase loss of phosphate in urine
Since calcium is being absorbed phosphate needs to be removed or it will react with calcium and form calcium hydroxyapatite
