Uremic pruritus: roles of parathyroid hormone and substance P.
BACKGROUND
Most patients receiving maintenance hemodialysis have pruritus, but its underlying mechanism remains unknown. Secondary hyperparathyroidism is another common problem in these patients, but its role in uremic pruritus is controversial. Capsaicin can deplete substance P from the peripheral neurons and is known to be effective in the treatment of pain and itching.


OBJECTIVE
Our purpose was to evaluate the role of parathyroid hormone (PTH) and substance P in uremic pruritus and to elucidate the underlying mechanisms.


METHODS
The study contained two phases. In phase I, we analyzed the correlation between the intensity of itching and serum levels of intact PTH. In phase II, patients with moderate to severe pruritus were placed into two groups: one with high PTH levels and one with low levels. A double-blind, placebo-controlled study of capsaicin 0.025% cream was conducted in phase II.


RESULTS
Serum levels of intact PTH did not correlate with the intensity of pruritus and did not significantly change during treatment with capsaicin or placebo. Capsaicin was significantly more effective in alleviating uremic pruritus than the placebo, and no serious side effects were noted.


CONCLUSIONS
Uremic pruritus is not related to PTH. Substance P may act as a neurotransmitter in uremic pruritus and topical capsaicin can be used in the treatment of localized pruritus.
Cho
Y L
YL
Department of Dermatology, National Yang-Ming University, Taipei, Taiwan.
Liu
H N
HN
Huang
T P
TP
Tarng
D C
DC
D002118:Calcium / Q000097:blood; D002211:Capsaicin / Q000627:therapeutic use; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood; D011537:Pruritus / Q000097:blood* / Q000188:drug therapy; D006435:Renal Dialysis / Q000009:adverse effects*; D013373:Substance P / Q000097:blood
D010281:Parathyroid Hormone; D010710:Phosphates; D013373:Substance P; D002211:Capsaicin; D002118:Calcium