Hypertrophy and hyperplasia
How tissues answer more work or more growth signals: by enlarging their cells (hypertrophy), by making more cells (hyperplasia) or both; why the heart can only enlarge its cells, and when growth becomes harmful.
By the end, you can
- Distinguish hypertrophy from hyperplasia, and explain why a tissue’s ability to divide decides which occurs.
- Explain how a pressure or volume load makes heart muscle cells enlarge, and what that costs.
- Give examples of physiological and pathological hyperplasia, hormonal and compensatory.
- Explain why some pathological hyperplasias raise the risk of cancer while others do not.
- Recognise pseudohypertrophy, and the gross and microscopic signs of hypertrophy and hyperplasia.
- Recognise the classic appearances, classifications and tests of cardiac hypertrophy and of prostatic and endometrial hyperplasia, and explain how removing the load or the hormonal drive makes them regress.
What it is
Hypertrophy is an increase in the size of cells, and so of the organ, from more structural proteins and organelles; no new cells are made. Hyperplasia is an increase in the number of cells, by division, and is possible only where cells can still divide. Both are adaptations to more demand or more growth signals, they often occur together, and either can be physiological or pathological. Unlike a tumour, both stop when the stimulus stops.
5 types to tell apart
- Work (compensatory) hypertrophy
- Cells enlarge to meet a sustained load: skeletal muscle with strength training, the left ventricle against high blood pressure or a narrowed aortic valve, the bladder behind an obstructed outlet.
- Vicarious (substitutive) growth
- When one of a pair of organs is lost, the other enlarges to take over its work, as the remaining kidney does, mainly by enlarging its tubular cells.
- Hormonal hyperplasia and hypertrophy
- Hormones drive growth: the breast at puberty and in pregnancy, the endometrium each cycle, and the pregnant uterus, mostly by enlargement of its smooth muscle cells.
- Pathological hyperplasia
- Too much of a hormone or growth factor, or a virus: endometrial hyperplasia, benign prostatic hyperplasia, the thyroid in Graves disease, skin warts.
- Pseudohypertrophy (false hypertrophy)
- An organ enlarges while its working cells are replaced by fat or fibrous tissue, as in the calves in Duchenne muscular dystrophy. It is not a growth adaptation.
US spelling: tumour → tumor, fibres → fibers.
Normal function
Which cells can divide
Tissues differ in whether their cells can re-enter the cell cycle. Labile cells divide throughout life (the epidermis, the gut lining, the bone marrow). Stable cells rest but divide when stimulated (hepatocytes, kidney tubule cells, fibroblasts, smooth muscle, the endometrium). Permanent cells have essentially left the cycle (adult heart muscle cells, skeletal muscle fibres and neurones).
That capacity decides how a tissue grows when demand rises: permanent cells can only enlarge, while labile and stable cells can multiply as well. In the heart, joined end to end at each hold one or two central . Adult heart muscle cells are renewed so slowly that the heart’s muscle grows by enlarging them.
| Feature | Hypertrophy | Hyperplasia |
|---|---|---|
| What increases | Cell size | Cell number |
| Needs cells that divide | No | Yes (labile or stable cells) |
| Typical tissues | Heart and skeletal muscle | Endometrium, breast, liver, prostate, skin |
| Physiological example | Muscle with training | Breast in pregnancy; endometrium each cycle |
| Pathological example | Left ventricle in high blood pressure | Endometrial and benign prostatic hyperplasia |
Many tissues use both together, such as smooth muscle of the pregnant uterus and the bladder.
Underlying change · Step 1 of 5
Hypertrophy: bigger cells, not more of them
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Hyperplasia: more cells
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
Often both at once: the remodelled airway
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
When the heart outgrows its supply
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Where growth can lead
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .