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 neonatal hypocalcemia  



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Author7 Posts
  #1

Hi guys.I was going through paeds and read that maternal HYPERparathyroidism is a reason for newborn hypocalcemia.can anyone explain why???




  #2

If hyperparathyroidism is causing hypocalcemia should be a typo.
If hyperparathyroidism is a reflection of ongoing hypocalcemia then it makes sense, as PTH is a hormone necessary to maintain serum calcium levels. It's called secondary hyperparathyroidism.


  #3

let's take 2 situations: first one when the baby is not born and second one when baby was born

on the first situation: mom produces PTH in excess due to her parathyroid hyperfunction....her PTH will pass placenta and in baby's blood will have the same effect like baby's own PTH; but because mother PTH is more than what the baby needs, baby's parathyroid function will be inhibited(negative feedback) which means the total baby's PTH is mainly from mom.....

on the second situation: the baby is born; right at this time she/he will still have extra PTH from mom; after a while this PTH from mom will dissapear(no more connection through placenta); as a consequence, total baby's PTH will drop and the baby will have hypocalcemia because baby's parathyroids are still inhibited by mother PTH(until baby's parathyroid kick's in takes a little while); this hypocalcemia should be a temporary one until baby's parathyroid kick's in and produces his/her own PTH;

if you understand this priciple, then you could very easy answer why the baby's who are born from DM mothers have hypoglycemia in their first days of life.....DM=too much glucose in blood; will pass into baby's blood and baby's pancreas will start to produce insulin way too much for his/her needs; once the placenta is removed, there is no more glucose from mom and the extrainsulin already secreted will give hypoglycemia.....


  #4

I checked this topic because on one hand I couldn't picture really well the causes of hypocalcemia in a generic newborn and as I understand, hypocalcemia is a very common issue. And I wasn't satisfied with my answer because I wondered that nobody has requested a PTH from a newborn, getting a high PTH with a low calcium still doesn't tell you much. Upon reading anatomie's superb explanation I realized I needed a good revision of this topic.

OK.
Neonatal hypocalcemia is classified as early (up to the 2nd day since birth) or late (>3rd day).

In addition there are some definitions:
>1500 grams of body weight (term infants/premature infants): hypocalcemia is defined as a total sCa < 8 mg/dL; ionized of 4.4 (or 1.1 mM)

<1500 grams of weight (premature infants): hypocalcemia is defined as a total sCa < 7 mg/dL; ionized of 4.4 (or 0.9 mM)

The causes are pretty sterotyped:

Early hypocalcemia (0-2 days):
-Prematurity (even if the total Ca is low the ionized Ca is not so low)
-Infants of Diabetic Mothers (associated with hyperphosphatemia)
-Birth Asphyxia (hyperphosphatemia too)
-Intrauterine growth retardation (possibly due to decreased transfer across the placenta)

LATE hypocalcemia (>2 days -end of first week).
Due to hypoparathyroidism are:
-DiGeorge Syndrome and Catch-22 syndrome
-Maternal Hyperparathyroidism, the mechanism is like anatomie explained except that there's no transfer of PTH from the mother, is calcium the one transfered. So it's maternal HYPER with baby's HYPO. What i found interesting is that this mechanism is considered LATE, so it means that the baby calcium levels take a long while to decrease and they maintain its own PTH inhibited during this time.
-Hypomagnesemia. If the Mg is low so is the PTH.
-High Phosphate intake. If given cow's milk or formula based on cow's milk. Rare in the U.S.
-Miscelanea (due to infusions to the baby) such as bicarbonate, transfusion with citrated blood, lipid infusions and last, phototherapy induced hypocalcemia (mild); acute renal failure, any disorder of Vitamin D metabolism, rotavirus infection.

In conclusion, the HYPERparathyroidism of the mother associated with the HYPOparathyroidism of the baby and thus hypocalcemia is considered to appear late after birth, and is only one among many other causes of hypocalcemia among which hyperphosphatemia stands out. The frequency probably of hypoCa is dependent on the prevalence of prematurity and DM. I don't know how frequent is mother's hyperparathyroidism (primary?).

In conclusion, the physiological scenario that i provided initially on the baby's PTH going up to control ongoing hypocalcemia appears to occur rarely in the neonate. But this mechanism is the main one for later in life.

Well, this helped me.


  #5

Thanksa lot anatomie and xenopus.didnt just get my doubt cleared,got to know so much more abt this topic


  #6

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  #7

@xenopus: thanks a lot....i did not know that PTH does not pass the placenta; so it's calcium who inhibits baby's parathyroids; every day we learn something.....one more time thank you!





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