An international study has identified a unique pair of genetic variants that can cause the sudden onset of high blood pressure in pregnant women.
The condition, called primary aldosteronism, causes sudden onset high blood pressure via increased production of the hormone aldosterone, can occur without warning during early pregnancy. This type of hypertension is often resistant to conventional treatments.
'What was particularly satisfying is that recognition of the cause of hypertension in these women enabled them to complete a successful pregnancy,' said one of the study authors, Professor Morris Brown, professor of endocrine hypertension at Queen Mary University of London (QMUL).
High blood pressure affects around 30 percent of adults and is usually due to a combination of genetic and acquired factors. For some people, the cause is a benign nodule in an adrenal gland. Found above the kidneys, adrenal glands produce the hormone aldosterone that stimulates sodium reabsorption in the kidneys and increases blood pressure. The excessive release of aldosterone leads to primary aldosteronism, which causes hypertension and is linked to a high risk of stroke, heart attacks and other complications.
The research, led by scientists at QMUL and St Bartholomew's Hospital, London, in collaboration with the Paris Cardiovascular Research Centre in France, describes a type of primary aldosteronism caused by the coincidence of a unique pair of gene variants occurring together.
The study, published in Nature Genetics, used a range of genomic and protein expression analyses in adrenal nodule tissues taken from patients with primary aldosteronism to show why women with these variants do not develop hypertension until they become pregnant.
When mutations are present in both G protein subunit genes α11 (GNA11) and Q (GNAQ), a receptor in the adrenal cells responds to the presence of the pregnancy hormone human chorionic gonadotrophin (HCG) – the same hormone detected by pregnancy tests – triggering increased aldosterone production.
After the women had given birth 'they were completely cured of hypertension by a procedure to remove the adrenal nodule, and were able to stop all their drugs' said Professor Brown.