General pathology · Cell injury, adaptation and death
Atrophy !
- Process
Atrophy is shrinkage of cells and organs when they get less work, blood, nerve supply, food or hormones.
Updated 2026-11-01
What it is
Atrophy is a decrease in cell size, and often number, due to loss of substance. The cell lowers its demands to survive: it makes fewer proteins and destroys more of them through the ubiquitin–proteasome system and autophagy. It can be physiologic (thymus after childhood, uterus after delivery) or pathologic (disuse, denervation, ischemia, malnutrition, loss of hormones, pressure).
Step by step
- The cell receives less stimulus, nutrition or oxygen.
- Growth signals (insulin, IGF-1) decrease and protein synthesis falls.
- Ubiquitin ligases tag structural proteins for destruction by the proteasome.
- Autophagy digests organelles; undigested remnants accumulate as lipofuscin.
- Cell size falls to a new balance; with prolonged loss, cells die by apoptosis.
Causes of pathologic atrophy
| Cause | Example |
|---|---|
| Disuse | Muscles in a cast or prolonged bed rest |
| Loss of innervation | Muscle atrophy in amyotrophic lateral sclerosis or nerve injury |
| Reduced blood supply | Cerebral atrophy with chronic small vessel ischemia |
| Inadequate nutrition | Marasmus and cancer cachexia |
| Loss of endocrine stimulation | Endometrium, vagina and breast after menopause |
| Pressure | Renal cortex in hydronephrosis; tissue next to a slow-growing mass |
Clinical notes
- Exogenous glucocorticoids suppress ACTH and cause atrophy of the adrenal cortex; stopping them suddenly can cause adrenal insufficiency.
- Sarcopenia, the age-related loss of muscle mass and strength, is a major cause of falls and frailty.
Test yourself
Think of the answer, then tap the question to see it.
Which proteolytic system is central to muscle atrophy?
The ubiquitin–proteasome system, with ligases such as atrogin-1 and MuRF1, together with autophagy.
Why can long-term glucocorticoid therapy cause adrenal atrophy?
The exogenous hormone suppresses ACTH, so the adrenal cortex loses its trophic stimulus.
What pigment accumulates in atrophic cells and gives brown atrophy?
Lipofuscin, made of undigested lipid peroxidation products.
Related
- Hypertrophy: physiologic and pathologic
- Autophagy
- Pigments in tissue: lipofuscin, hemosiderin, melanin, bilirubin, carbon
- Cellular aging: telomeres, DNA damage, senescence and proteostasis
- How organs age: normal changes vs disease
- Cachexia, anorexia nervosa and bulimia
Related conditions
- Sarcopenia
- Alzheimer disease
- Frontotemporal dementia
- Marasmus
- Spinal muscular atrophy
- Amyotrophic lateral sclerosis
- Immobility syndrome and hospital-associated deconditioning
- Genitourinary syndrome of menopause (atrophic vaginitis)
- Hydronephrosis and obstructive uropathy
- Adrenal insufficiency
- Critical illness polyneuropathy and myopathy (ICU-acquired weakness)
- Vascular dementia
Elsewhere in DurgiPedia
- Cell adaptations: hypertrophy, hyperplasia, atrophy, metaplasia
- Muscle hypertrophy, atrophy and remodeling
- Prolonged fasting and starvation
- Menopause
- Ubiquitin–proteasome system
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Muscle atrophy: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2024); Aging changes in organs, tissue and cells: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2024).
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Representative model, for educational purposes only.