Endocrine Manifestations of Non-Endocrine Diseases

Non-endocrine diseases—especially malignancies—can cause significant hormonal dysregulation, often through paraneoplastic syndromes. These effects may mimic primary endocrine disorders, making diagnosis and management more complex.

Mechanisms of Endocrine Disruption:

Paraneoplastic hormone secretion (e.g. ↑ADH, ↑PTHrP)
Tissue infiltration (e.g. adrenal glands in TB or lymphoma)
Organ dysfunction (e.g. CKD → ↓vitamin D, ↑PTH)
Inflammatory cytokines disrupting hormonal axes

System / Disease Group	Associated Conditions & Endocrine Effects	Clinical Relevance for GPs
Malignancies	- SCLC (small-cell lung cancer) → SIADH (↓Na⁺), ectopic ACTH (Cushing’s) - Breast, lung, head & neck cancers → PTHrP secretion → ↑Ca²⁺ - Lymphoma → direct adrenal infiltration (Addison's)	Monitor for weight loss, electrolyte imbalance, or features of cortisol excess. Early recognition can lead to cancer diagnosis. Refer to oncology/endocrinology.
Infections & Inflammatory Disorders	- TB, HIV, fungal infections → adrenalitis → adrenal insufficiency - Post-viral (e.g. COVID-19) → subacute thyroiditis - Chronic HIV → hypogonadism (↓testosterone)	Consider in fatigue, ↓Na⁺, hypotension, or hyperpigmentation. Screen for HIV/TB in high-risk groups. Start steroids if Addison’s suspected.
Gastrointestinal & Nutritional Disorders	- Coeliac disease → autoimmune thyroid disease, ↑T1DM risk - IBD, chronic pancreatitis → ↓vitamin D → ↑PTH, osteoporosis - Severe malnutrition → ↓TSH, adrenal axis...

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