There are two cases in which a lung cancer can lead to hyper pigmentation in skin:
1. Metastasis:
- Adrenals are the most common site of metastasis for a lung cancer
- Lung cancer metastasizes to the adrenals
- Destroyed adrenal cortex
- Decreases cortical hormones
- Decreased cortisol in turn increased hypothalamic CRH production (Negative feedback)
- That leads to increased pituitary proopiomelanocortin (POMC) production and breakdown
- Breakdown of POMC yields beta MSH, beta endorphin and ACTH
- MSH (little) and ACTH (mainly) increase melanin content of the skin
- Increased melanin in skin leads to hyper pigmentation
This case is more like Addisons because adrenal cortex is destroyed by malignancy.
2. Ectopic ACTH
It can produce hyperpigmentation rarely because
- The disease course is not long enough
- ACTH structure may differ from that produced in pituitary as POMC is produced only in pituitary including specific amino acids in pituitary ACTH that are necessary for their action in skin receptors
This case is more like Cushings because the adrenal cortical hormones increase due to ectopic ACTH.
By Doctor
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