calcitonin

[DrJMR]

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While calcitonin is the antipode of parathyroid hormone (PTH) in those actions, it is not dissimilar from PTH in its effect on electrolyte reabsorption in the kidneys. Namely, calcitonin:

• Inhibits phosphate reabsorption by the kidney tubules[7]
• Calcitonin increases tubular reabsorption of Ca2+, leading to decreased rates of its loss in urine.[7]

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Calcitonin acts to lower blood Ca concentration. If that is the case, wouldn't an increase in tubular reabsorption lead to INCREASED rates of loss in urine?
If Ca levels were high, wouldn't we want to decrease them by increasing excretion of Ca in the urine by the actions of the kidneys?

I read the research reference associated with this, but can someone explain this so I can understand intuitively why calcitonin and PTH would both increase tubular reabsorption?

Thanks for your input!

 

[cartman1980]

maybe my understanding is flawed but i thought
- calcitonin (secreted by Thyroid gland) lowers serum [Ca2+] concentrations by a) decreasing bone resoprtion b) increasing renal [Ca2+] excretion

- PTH (secreted by Parathyroid gland) acts opposite to calcitonin by a) increasing bone resorption b) increasing [Ca2+] renal absorption
c) assists in formation of Vitamin D which inturn increases [Ca2+] absoprtion in intestines and increases [Ca2+] renal absoprtion

 

[gunj122]

this is very weird and contradictory. in the BR Biology part I book, section V, passage #8, the last sentence reads:

"Calcitonin acts to inhibit osteoclast activity and reduce bone resorption. This hormone also inhibits calcium and phosphate reabsorption in the kidney and increases the excretion of these ions in the urine."

after reading the abstract for the research article, im all the more confused.