Posted by tealady on November 2, 2004, at 3:32:11
In reply to Vitamin D and depression, posted by JLx on November 1, 2004, at 17:27:18
Hi JL,
Just lost my post, sigh and don't have time to redo.. haven't read your posts but my view differs from Lar..
haven't really looked at closely though
Personally if I was you I wouldn't go overboard on VitD(considering your calcium stone history)..and yes, it is probably possibly to overdose from sunlight but most peope tend to burn and move out of the sun after a while<g>Below is copy and paste
------------------------------
Vitamin D is a prohormoneAlthough vitamin D is nutritionally essential for people who stay out of the sun, it can be synthesized photo-chemically in the skin, and with even mild sun exposure there is no need for a dietary source. Vitamin D is synthesized from 7-dehydrocholesterol, which is present in small amount in all tissues. This steroid is photochemically cleaved to cholecalciferol (vitamin D3) by radiation in the UV range.
The cholecalciferol formed in the skin is transported in tight noncovalent binding to a vitamin D- binding plasma protein. Cholecalciferol is converted to 1,25-dihydroxycholecalciferol (calcitriol) by successive hydroxylations in liver and kidney. Calcitriol is the major physiologically active form of vitamin D. 25-Hydroxylation in the liver is not rate limiting, and therefore 2s-hydroxycholecalciferol (25-OH-D3), which is also bound to the D-binding protein, is the major circulating form of the vitamin. The 1α-hydroxylase in the kidney, however, is tightly regulated: its activity is increased by parathyroid hormone (PTH), by hypocalcemia, and by hypophosphatemia. Cholecalciferol and 25-OH-D3 have biological half-lives on the order of 30 days, but calcitriol lives for only 2 to 4 hours.
Calcitriol is a hormone-like substance. Its receptor is a ligand-regulated transcription factor that belongs to the same superfamily as the receptors for retinoic acid, steroid hormones, and thyroid hormones. Calcitriol upregulates the plasma calcium concentration, an effect that it shares with PTH. In bone, it facilitates the resorption of calcium and phosphate by stimulating osteoclasts, acting cooperatively with PTH in this tissue. In the intestine, it stimulates the absorption of dietary calcium and phosphate, without the aid of PTH. In the kidney it stimulates calcium reabsorption, again in cooperation with PTH.
The plasma calcium level is regulated very tightly. In acute hypocalcemia, PTH restores the plasma calcium level within minutes by stimulating osteoclasts and inducing the release of calcium and phosphate from bone. It also boosts calcitriol formation by stimulating the renal 1α-hydroxylase. While PTH acts on bone to maintain the plasma calcium level on a minute-to-minute basis, calcitriol acts on intestine and kidney to increase the total amount of calcium and phosphate in the body.
Vitamin D deficiency is called rickets in children and osteomalacia in adults. The immediate effect is a decrease of the plasma calcium concentration.This hypocalcemia is compensated by an increased release of PTH, which rapidly restores plasma calcium to near-normal levels. Even in long-term vitamin D deficiency, the plasma calcium level can be
maintained by PTH-- at the expense of the bones, which are tapped as a calcium reservoir and gradually are depleted of their mineral content. PTH also reduces the level of circulating phosphate by inhibiting renal phosphate reabsorption. More than 99% of our calcium and phosphate is in the extra-cellular matrix of bone, and the depletion of total body stores of calcium and phosphate in vitamin D deficiency leads to soft, poorly mineralized bones that bend rather than break under stress.Although rickets used to be common in cloudy countries, notably England, it is now rare. In the absence of sunlight, a daily intake of 5 to 10 microgram (200 to 400 IU) of cholecalciferol is considered adequate. Vitamin D is present in only a few natural foodstuffs, including liver, egg yolk, and saltwater fish (cod liver oil!), as well as in fortified foods. The synthesis of cholecalciferol in the skin is affected by skin color: white skin produces approximately five times more vitamin D than black skin does. The protection from rickets is thought to be the main advantage of white skin in those human races that evolved in cloudy climates.
Calcitriol has been found effective in the treatment of osteoporosis, a common cause of pathological fractures in the elderly. Vitamin D actually may be involved in the etiology of this ailment: the calcitriol receptor occurs in two common allelic variants - B and b - in the population, and homozygosity for the B allele is associated with a high risk of the disease.
Hypervitaminosis D, caused by the overuse of vitamin D supplements, leads to rampant hypercalcemia, hypercalciuria, and metastatic calcification. The toxic state persists for a few months after discontinuation of the offending agent if the overuse of cholecalciferol is the cause, but it lasts for only a week or so if toxicity is caused by calcitriol. Chronic hypercalcemia can result in irreversible cardiovascular and renal damage.
------------------------------------http://www.eamg-med.com/members/encyclopedia/12/12_11.shtml
Lithium, used in manic depressive disorders, is a goitrogenic agent which acutely blocks iodine uptake and the release of thyroid hormones. Only 2 per cent of patients on lithium actually develop clinical features of hypothyroidismParathyroid
Lithium therapy can cause an increase in parathyroid gland size, either with hyperplasia or adenoma. This hyperparathyroidism leads to mild hypercalcaemia and sometimes osteoporosis. Thiazide diuretics, by causing haemoconcentration and hypocalciuria, may also result in mild hypercalcaemia but this is usually transient (4-6 weeks); after this time, other causes of hypercalcaemia should be sought.
Vinblastine and colchicine inhibit parathyroid hormone secretion which may result in hypocalcaemia.---------------------------------
my thoughts added
and colchicine is in gingko ..so gingko and lithium may tend balance out each other to an extent in their effect on the parathyroids.Jan cya
Oh yes, have a look in Ganaong (google in my posts for ref..available oon net for free)..haven't read as yet but sure to have a lot of stuff on..and all uptodate too
poster:tealady
thread:410247
URL: http://www.dr-bob.org/babble/alter/20041022/msgs/410453.html