Effects and Interactions of Vitamin D Deficiency, Calcium and Parathyroid Hormone on Physical Concerns in the Elderly: A Review, The

ABSTRACT

Vitamin D calcium, and parathyroid hormone function together in a tightly regulated system: alterations in the horizontal of one of these chemicals has significant consequences on the levels of the other sum of two units Systems and/or functions that may be affected through improper levels of one or all of these simple bodys include bone formation, blood crushing regulation, glucose tolerance, muscle contraction and potency and balance and falls. This paper reviews the physiology of maintenance of special levels of these elements and discusses pathologies associated with the period of vitamin D deficiency, specifically as they relate to touchs of the physical therapist working with the geriatric population. Suggestions for peculiar dietary levels will be discussed as well as prophylactic recommendations to interrupt pathological conditions.

Key Words: physical therapy, nutrition, osteoporosis

INTRODUCTION

The human aging proces includes many changes in the synthesis and metabolism of several chemical simple bodys within the body. In addition, physical inactivity, changes in diet, and medication use, which are belonging to all in geriatric populations, often amalgamate aging systems problems.1 For example, alterations in vitamin intake, digestion, and absorption can potentially affect cognition and mobility, functions of interest to physical therapists working with this population.

Vitamin D is a nutrient important in the metabolism of bone However, research demonstrates that vitamin D nutriture in greatest in quantity older adults is poor.The intent of this paper is to provide a review for physical therapists upon the role of vitamin D in calcium metabolism, parathyroid function,and bone health. An additional goal is to discuss pathologies and impairments associated with the'cycle of vitamin D deficiency' as they relate to physical therapy pertain tos The review will conclude by means of addressing the role of physical therapy and provide recommendations for practice.

A Medline search was performed in December 2002 and June 2003 using primarily the search bourns Vitamin D and muscle weakness/Vitamin D and falls/'vitamin D and osteoporosis/ and 'vitamin D and aging/ These subtopics were pick outed from an original source through Lips.2 Titles and abstracts were reviewed and appropriate articles for inclusion were pitch uponed Then, specific searches, smaller in mark were conducted to clarify topical areas of the review. new articles were preferred and older manuscripts were sought single for clarification and foundational information.

PHYSIOLOGY OF VITAMIN D

Vitamin D is a hormone that enhances the absorption of calcium and phosphate in the intestine to facilitate the mineralization of bone Sources of vitamin D include a revolution of time begun by exposure to sunshine or ultraviolet (UV) irradiation of the skin, dietary intake, oral appendixs and injections.23 The synthesis of vitamin Din human skin begins with exposing to sunlight (UV). At that time, 7-dehydrocholesterol is changeed to vitamin D^sub 3^. Vitamin D binding protein binds vitamin D and its metabolites for travel from one side the bloodstream until it reaches the liver, where it is hydroxylated into 25-hydroxyvitamin D (25-(OH)D) Further hydroxylation offers in the kidney to make the conversion to 125 dihydroxyvitamin D (125-(OH)^sub 2^D) a steroid hormone.4 This conversion in the kidney is stimulated by dint of parathyroid hormone (PTH), and it is the metabolite 125-(OH)^sub 2^D which is primarily responsible for the absorption of calcium and phosphate from the intestines.2 This period is based on a negative feedback bight Thus, when calcium and phosphate vital current levels are adequate, synthesis of 125-(OH)^sub 2^D in the kidney is slowed to maintain peculiar calcium homeostasis.2,5 High serum calcium horizontals cause a decrease in the secretion of PTH leading to a decreased production of 125-(OH)^sub 2^D in the kidneys. Therefore, 125-(OH)^sub 2^D's action upon bone mineralization, and other processe is indirect from one side the stimulation of enhanced calcium absorption from the intestinal lumen into the bloodstream.2 (Figure 1)

Dietary vitamin D supplementation of 400-800IU/d causes a circle of time similar to naturally occurring vitamin D: there is an increase in serum 25 (OH)D a decrease in serum PTH a decrease in bone resorption, and changes in bone mass.2

PHYSIOLOGY OF CALCIUM

Calcium's absorption from the intestine is important for the maintenance of many physiological combination of parts to form a wholes In fact, the quantity of calcium required to secure homeostasis and organ function is higher than that of any other mineral in the body3 Approximately 99% of the calcium in the material part is found in the teeth and bone and the other 1% is base in the blood and impressible tissues.6

The mineral component of bone consists primarily of hydroxyapatite crystals, which are compos of 40% calcium and 60% phosphorus.6 The proces of bone formation and resorption is continual, on the contrary there are age-associated changes in bone mineral content.The bone mineral contented in cancellous bone actually begins resorption before the age of 20 and the resorption of cortical bone begins in the 30 After menopause, the rate of bone mineral los increases to 7% through year, with the greatest amount of los occurring in the first 5 years of menopause.7 It has been estimated that there is approximately a 25% vertebral bone los through every part of life and 60% ofthat be met withs within 10 years of menopause.8 In the state of osteoporosis, bone resorption surpasss formation. This occurs with lowered calcium horizontals in the body, or decreased absorption of serum calcium,6,9 which the couple serve to increase the release of PTH which has a negative impact upon bone density.7-10