Prolonged Low‐intensity Exercise Raises the Serum Parathyroid Hormone Levels

Abstract

Twelve healthy males performed 5 h exercise on a bicycle ergometer at a constant work load of approximately 50% of their maximum capacity. The serum concentrations of parathyroid hormone (PTH) increased after the first hour and were continuously elevated throughout the exercise period. The rise in PTH was 5-7% above pre-exercise levels, corresponding to 20-30% of the maximal increase obtained by the same assay during prolonged hypocalcaemia. The probable cause for the rise in PTH was that the plasma ionized calcium tended to be lowered during exercise. Since the total serum calcium concentrations were raised (by 3-5%) during exercise the reduction of the free, ionized, fraction was presumably largely due to increased complex-binding although an outward transport from plasma was not excluded. The serum concentrations of magnesium were gradually reduced during exercise while those of phosphate and potassium were raised throughout, probably as a result of leakage from the working muscle.

The effects of brisk walking on markers of bone and calcium metabolism in postmenopausal women

“…Previous studies at our institution have shown that moderate endurance exercise of the same intensity induces a significant decrease in the concentrations of ionized calcium and concomitant increases in the concentrations of PTH in young, untrained females (K. Thorsen, in preparation). Furthermore, other investigators have shown that moderate exercise affects calcium homeostasis [26] and serum levels of osteocalcin [29]. Another explanation for why no such alterations were observed in this experiment might be that menopause (or age) induces a relative insensitivity to moderate physical activity on calcium homeostasis.…”

“…Exogenous estrogen protects against bone loss after menopause and some of the possible mechanisms by which estrogen acts, besides the direct effect on bone, are the modulation of PTH secretion or the resetting of the set point of PTH stimulation by ionized calcium [24,25]. It is well known that the concentrations of ionized calcium and PTH are altered by physical exercise in younger men [26]. To our knowledge, no such studies have been performed in elderly women.…”

Maintenance of Serum Ionized Calcium During Exercise Attenuates Parathyroid Hormone and Bone Resorption Responses

“…A , C ). The early increase reflected hemoconcentration caused by the contraction of plasma volume, which occurs within minutes and is sustained during exercise . Indeed, when adjusted for changes in plasma volume, iCa ADJ and tCa ADJ decreased by –0.7 and –1.3 mg/dL, respectively, in the first 15 min of exercise (Fig.…”

Hormonal Responses to Exercise and Training: A Short Review

“…Finally prolonged (5 h), low intensity exercise has recently been reported to cause a slight rise in serum PTH, associated with a small fall in plasma ionized calcium concentrations (Ljunghall et al, 1986).…”