Letter: Letters: Relief in pregnancy

From SAM MARTIN

Victor Gavin’s observation of his pregnant wife’s remission from asthma
(Letters, 12 December) may have an underlying hormonal basis.

The enzyme histidine decarboxylase is responsible for the single step
conversion of histidine to histamine, and in mice its activity, at least
in the kidneys, is induced both by oestrogen and during pregnancy. It has
been known since 1940 that blood and urine levels of histamine are extremely
high during human pregnancy.

Histamine is involved in a wide range of biological processes including
pregnancy, rapid growth (including reparative and malignant growth), and
the allergic response which, of course, includes asthma. Histamine is secreted
by mast cells in the lungs where its fundamental role in vasodilation may
explain its connection with relieving asthma in pregnant women.

By the way, I experienced temporary relief from chronic back pain throughout
both my pregnancies.

(Ms) Sam Martin Glasgow