August 1, 1977European Journal of Clinical Investigation
Vitamin A stimulation of parathyroid hormone: interactions with calcium, hydrocortisone, and vitamin E in bovine parathyroid tissues and effects of vitamin A in man
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Discussion
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Implication
Experimental study demonstrates vitamin A stimulates parathyroid hormone secretion in bovine tissue and humans, indicating a potential mechanism for toxicity in vitamin A excess.
Key Points
- To investigate the direct effects of vitamin A on parathyroid hormone secretion and lysosomal enzyme activity in vitro and assess its influence on circulating parathyroid hormone levels in humans.
- Incubated bovine parathyroid tissues with varying concentrations of vitamin A (retinol, 10⁻⁹ to 10⁻⁶ mol/l), retinoic acid, calcium, hydrocortisone (10⁻⁶ and 10⁻⁵ mol/l), and vitamin E (10⁻⁵ mol/l) to measure hormone secretion and lysosomal cathepsin D activity.
- Administered two intramuscular injections of vitamin A palmitate (25,000 units each) within 24 hours to 11 healthy men to monitor in vivo changes in serum parathyroid hormone.
- Vitamin A increased bovine parathyroid hormone release in a dose- and time-dependent manner across concentrations from 10⁻⁹ to 10⁻⁶ mol/l, while retinoic acid produced no stimulatory effect.
- High calcium concentration, hydrocortisone (10⁻⁶ and 10⁻⁵ mol/l), and vitamin E (10⁻⁵ mol/l) significantly antagonized vitamin A-induced hormone secretion, while vitamin A elevated lysosomal cathepsin D activity.
- Serum parathyroid hormone concentrations increased after vitamin A administration in all 11 healthy male subjects.
Cite This Study
Chertow et al. (1977) studied this question.