Low Blood Levels of Vitamin D May Be Associated With
Depression in Older Adults
May
5, 2008 - Older adults with low blood levels of vitamin D and high blood
levels of a hormone secreted by the parathyroid glands may have a higher
risk of depression, according to a report in the May issue of Archives
of General Psychiatry, one of the JAMA/Archives journals.
About 13 percent of older individuals have symptoms
of depression, and researchers have speculated that vitamin D may cause
this depression and other psychiatric illnesses.
Underlying causes of vitamin D deficiency such as
less sun exposure as a result of decreased outdoor activity, different
housing or clothing habits and decreased vitamin intake may be secondary
to depression, but depression may also be the consequence of poor
vitamin D status, the authors write.
Moreover, poor vitamin D status causes an increase
in serum parathyroid hormone levels.
Overactive parathyroid glands are frequently
accompanied by symptoms of depression that disappear after treatment of
the condition.
Witte J. G. Hoogendijk, M.D., Ph.D., and colleagues
at VU University Medical Center, Vrije Universiteit Amsterdam, the
Netherlands, measured blood levels of vitamin D and parathyroid hormone
and assessed symptoms of depression among 1,282 community residents age
65 to 95.
Of those individuals, 26 had a diagnosis of major
depressive disorder, 169 had minor depression and 1,087 were not
depressed. The average blood vitamin D level was 21 nanograms per
milliliter and the average parathyroid hormone level was 3.6 picograms
per milliliter.
Blood vitamin D levels were 14 percent lower in
individuals with major and minor depression (average, 19 nanograms per
milliliter) compared with non-depressed participants (average, 22
nanograms per milliliter).
In addition, parathyroid hormone thyroid levels
were an average of 5 percent higher in those with minor depression
(average, 3.72 picograms per milliliter) and 33 percent higher in those
with major depressive disorder (average, 4.69 picograms per milliliter)
than in those who were not depressed (average, 3.53 picograms per
milliliter).
The findings may be important to patients because
both low blood vitamin D levels and high parathyroid hormone levels can
be treated with higher dietary intake of vitamin D or calcium and
increased sunlight exposure.
Moreover, the clinical relevance of the present
study is underscored by our finding that 38.8 percent of men and 56.9
percent of women in our community-based cohort had an insufficient
vitamin D status, they conclude.
Additional studies are needed to determine whether
changes in levels of vitamin D and parathyroid hormone precede
depression or follow it.
Editor's Note: This study was supported by a
clinical fellow grant from the Netherlands Organisation for Scientific
Research.
More About Parathyroid Glands
The
parathyroid glands are four or more small glands located on the
posterior surface of the thyroid gland. Histologically they are quite
easily recognizable from the thyroid as they have densely packed cells
in contrast with the follicle structure of the thyroid. However at
surgery they are harder to differentiate from the thyroid or fat.
The sole function of the parathyroid glands is to
maintain the body's calcium level within a very narrow range, so that
the nervous and muscular systems can function properly.
When blood calcium levels drop below a certain
point, calcium-sensing receptors in the parathyroid gland are activated
to release hormone into the blood.
Parathyroid hormone (PTH, also known as
parathormone) is a small protein that takes part in the control of
calcium and phosphate homeostasis, as well as bone physiology.
May
5, 2008 - Older adults with low blood levels of vitamin D and high blood
levels of a hormone secreted by the parathyroid glands may have a higher
risk of depression, according to a report in the May issue of Archives
of General Psychiatry, one of the JAMA/Archives journals. 