Aging Alters the Endocrine System
LEARNING OBJECTIVE
1.
Describe
the effects of aging on the endocrine
system.
ging alters the secretions of various endo-
crine glands. Because several endocrine func-
tions involve more than one endocrine gland
through negative-feedback loops, aging may
cause different hormonal changes; some glands may in-
crease secretions, while others may decrease secretions.
InSight
O v e r v ie w o f t h e e f f e c ts o f a g in g
o n t h e m a jo r e n d o c r i n e g l a n d s
Figure 9.21
Most often, as we age, the secretions of
major endocrine glands diminish, and
some endocrine glands may shrink.
Female
Male
Pineal gland - Secretion of
melatonin is reduced with age,
which may disrupt normal
sleep-wake cycles.
Hypothalamus
• GHRH secretion from the hypothalamus
may also diminish with age.
• TRH secretion may be elevated due to
failure of negative feedback by thyroid hormones.
• Slightly higher levels of CRH due to
failure of negative feedback by cortisol.
• GnRH secretion decreases.
Pituitary gland
• hGH secretion decreases, leading to
muscle atrophy and weakness.
• TSH secretion may be elevated due to
negative feedback by thyroid hormones.
• Slightly higher levels of ACTH due to failure
of negative feedback by cortisol.
• LH, FSH secretions decrease probably due
to decreasing GnRH from hypothalamus.
The thymus gland shrinks significantly, resulting in
decreased immune cell production and decreased
resistance to disease.
Thyroid gland
• Thyroid hormone secretions diminish, resulting in
reduced rate of metabolism. A reduction in metabolism
encourages the formation of more body fat and
increases sensitivity to cold temperatures.
• Calcitonin secretion diminishes.
278 CHAPTER 9
The Endocrine System
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