Summary
Weight changes can have primary causes (i.e., change of caloric intake or change of physical activity) and can be physiologic or pathological. Unexpected weight changes can have various secondary causes including weight loss due to malignancy or weight gain due to hypothyroidism and are always pathologic.
Unexpected weight loss
Unexpected weight loss is the unintentional or involuntary decrease in body weight (i.e., without the use of certain drugs including thyroxine and diuretics, a decrease of calorie intake or an increase of physical activity) of > 5% of usual body weight over a time period of 6–12 consecutive months. It can be due to:
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Endogenous factors
- Malignancy (e.g., lung cancer, colorectal cancer)
- Endocrinopathies (e.g., hyperthyroidism, hypocortisolism, diabetes mellitus)
- Gastrointestinal conditions (e.g., gastritis, celiac disease, Crohn disease, ulcerative colitis)
- Conditions with organ failure (e.g., COPD, renal failure)
- Infectious diseases (e.g., tuberculosis, HIV)
- Inherited disorders (e.g., cystic fibrosis)
- Psychiatric conditions (e.g., schizophrenia, bipolar disorder, major depression)
- Exogenous factors: substance abuse (e.g., nicotine addiction, amphetamines use disorder, cocaine use disorders)
References:[1]
Unexpected weight gain
Unexpected weight gain is an unintended increase in body weight without an increase in calorie intake or a decrease in physical activity. Common causes of unexpected weight gain include:
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Endocrine changes
- ↑ Cortisol (associated with, e.g., Cushing syndrome, stress, depression, anxiety)
- ↑ Ghrelin/↓ leptin (associated with insomnia)
- ↑ Insulin (associated with insulinoma)
- ↓ Thyroid hormones (associated with, e.g., Hashimoto thyroiditis, iodine deficiency)
- ↓ Growth hormone (associated with, e.g., infection, brain tumors)
- ↑/↓ Estrogen (associated with, e.g., polycystic ovary syndrome, pregnancy, premenopause)
- Water retention
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Medication
- Antidepressants (e.g., mirtazapine)
- Corticosteroids (e.g., prednisone)
- Antipsychotics (e.g., risperidone)
- Beta blockers (e.g., labetalol)
- Insulin
- Antithyroid drugs (e.g., methimazole)
References:[2]