DR Medhat MRCP

Actions of parathyroid hormone
( plasma Ca from bones and kidneys and
activation of Vit-D)
■ Plasma calcium, plasma phosphate
■ Renal tubular reabsorption of calcium
■ Osteoclastic activity
■ Renal conversion of 25-hydroxy vitamin
D to 1,25 dihydroxy vitamin D
■ Renal phosphate reabsorption
Actions of vitamin D
( Plasma Ca from bones , kidneys and
GIT)
■ Plasma calcium and plasma phosphate
■ Renal tubular reabsorption and gut
absorption of calcium
■ Osteoclastic activity
■ Renal phosphate reabsorption
Unlike steroids (progesterone, testosterone, oestradiol and cortisol), the other ionic
hormones e.g Adrenaline, GHRH, glucagon, LH, FSH, PTH, and TSH are unable to pass the
plasma membrane→ act upon cell surface receptors and then through cAMP as the
سؤال second messenger