Growth hormone production reduced in HIV-positive men with fat redistribution

The amount of growth hormone produced by HIV-positive men with fat redistribution is lower than in men without HIV and than in HIV-infected women with a similar age and body composition, according to a study published in the 4^th April edition of AIDS. The study also found that growth hormone production is lower in white patients than non-white patients.

Growth hormone is produced by the pituitary gland at the base of the brain and is responsible for normal growth and development in the body. Patients with fat redistribution as a side-effect of HIV treatment are thought to be at risk of deficiencies in growth hormone production. This has resulted in growth hormone being tested as a treatment for body fat redistribution, along with other factors than can stimulate the body to increase its growth hormone production, to reduce their risk of cardiovascular disease.

Gender is known to affect the levels of growth hormone production among HIV-negative patients, but its effect in HIV-positive patients has not been assessed. The impact of race on the production of growth hormone is also poorly understood in patients with HIV.

Accordingly, doctors from Massachusetts General Hospital in Boston wished to examine the effects of gender, race and fat redistribution on growth hormone production among HIV-positive patients. They hoped that this would allow them to work out which patients are at risk of low growth hormone production. This may help the identification of patients who will benefit from growth hormone treatment and avoid the risk of the hormone’s side-effects by giving it to patients who do not need it.

The team of doctors measured growth hormone levels in 139 men and 25 women in response to a standard testing protocol consisting of growth hormone releasing hormone and arginine injections. All of the patients had evidence of fat redistribution after at least twelve weeks of stable antiretroviral therapy.

The doctors found that the women in the study had higher levels of growth hormone production than the men. This was reflected both in the peak levels of growth hormone that were detected (mean 36.4 vs. 18.9 ng/ml; p < 0.001) and in the total production of growth hormone over a two-hour measurement period (mean 2679 vs. 1284 mg.min/dl; p < 0.001).

When they looked at the effects of race, the investigators found that Caucasian men had lower total production of growth hormone than non-Caucasian men (mean 1146 vs. 1831 mg.min/dl; p = 0.04), although the peak growth hormone levels were not statistically different.

However, race was not linked to growth hormone production in the HIV-positive women.

“HIV-infected men with fat redistribution have significantly reduced growth hormone peak responses and increased failure rates to standardised growth hormone testing in comparison to healthy male control subjects and to HIV-infected women of similar age and body mass index,” the investigators conclude. “Growth hormone secretion is related to gender and race in HIV-infected patients.”

The group of doctors also wished to work out a cut-off value to define growth hormone deficiency in HIV-positive patients. By comparing the peak growth hormone levels between their cohort of HIV-positive patients and a control group of 51 HIV-negative people of similar age, body mass relative to height and race, they found that a cut-off of 7.5ng/ml was optimal for men.

“The cut-off of 7.5 ng/ml provided the optimal separation between the HIV and control groups, while maintaining good specificity, i.e. less than 10% of the controls failed,” write the investigators. “Using this cut-off approximately one third with fat redistribution fail the growth hormone releasing hormone plus arginine test, and this can be considered at least relatively growth hormone deficient.”

However, they were unable to calculate a suitable cut-off value for the women in the study, as the HIV-positive and -negative women had similar rates of failure when they tested a range of cut-off values for peak growth hormone levels.

The investigators found that growth hormone production was unaffected by use of different types of anti-HIV drugs in either sex or by menstrual status in HIV-positive women. However, the degree of growth hormone deficiency was linked to the ratio of waist to hip size, a marker of fat gain around the central organs in HIV-positive men.

This study’s findings indicate that taking race, waist to hip ratio and the response to the growth hormone releasing hormone plus arginine test can help doctors identify which HIV-positive men may benefit from growth hormone treatment. However, it failed to draw strong conclusions on which women would benefit from growth hormone treatment.

“Further studies with larger numbers of women will be necessary to investigate growth hormone responses in HIV-infected women and the need for growth hormone augmentation in this population,” the investigators write.