PTH And Calcium Responses to Exercise (PACE) in Older Adults
PTH And Calcium Responses to Exercise (PACE) in Older Adults
Exercise that causes a decline in serum Calcium (Ca) as a result of dermal Ca loss stimulates
 bone resorption via an increase in Parathyroid Hormone (PTH).
Determine whether the magnitude of dermal Ca loss (i.e., sweating) during exercise is a
 determinant of the decline in iCa and increases in PTH and carboxy-terminal collagen
 crosslinks (CTX; marker of bone resorption). The proposed experiment will address this by
 manipulating the rate of dermal Ca loss (moderate vs high sweating rate) to determine whether
 this is the trigger for the cascade described in Figure 1. This will be achieved by having
 participants perform two identical exercise bouts under different thermal conditions (warm vs
 cool).
Inclusion Criteria:

 -  Healthy adults aged 60-80 y

 Exclusion Criteria:

 -  Use of medications in the past 6 months known to affect bone metabolism (e.g.,
 bisphosphonates, thiazide diuretics, oral glucocorticoids)

 -  BMD t score < -2.5 at the total hip or lumbar spine

 -  Known disease or condition associated with intestinal malabsorption

 -  Moderate or severe renal impairment defined as an estimated glomerular filtration rate
 of <60 mL/min/1.73m2 based on the MDRD equation

 -  Chronic hepatobiliary disease, defined as liver function tests (AST, ALT) >1.5 times
 the upper limit of normal; if such values are obtained on initial screening and
 thought to be transient in nature, repeated testing will be allowed

 -  Thyroid dysfunction, defined as an ultrasensitive TSH <0.5 or >5.0 mU/L; volunteers
 with abnormal TSH values will be re-considered for participation in the study after
 follow-up evaluation by the PCP with initiation or adjustment of thyroid hormone
 replacement

 -  Serum calcium <8.5 or >10.3 mg/dL

 -  Serum 25(OH)D <20 ng/mL; volunteers with abnormal serum 25(OH)D values may be
 re-considered for participation in the study if serum 25(OH)D is >20 ng/mL after
 vitamin D supplementation

 -  Uncontrolled hypertension defined as resting systolic BP >150 mmHg or diastolic BP>90
 mmHg; participants who do not meet these criteria at first screening will be
 re-evaluated, including after follow-up evaluation by the PCP with initiation or
 adjustment of anti-hypertensive medications

 -  History of type 1 or type 2 diabetes

 -  Cardiovascular disease; subjective or objective indicators of ischemic heart disease
 (e.g., angina, ST segment depression) or serious arrhythmias at rest or during the
 graded exercise test (GXT) without follow-up evaluation will be cause for exclusion;
 follow-up evaluation must include diagnostic testing (e.g., stress echocardiogram or
 thallium stress test) with interpretation by a cardiologist

 -  Diagnosis or history of asthma