Full text of DOI:10.1007/BF03343817

J. Endocrinol. Invest. 24: 78-82, 2001
Intestinal permeability in adult patients with growth
hormone deficiency
J. García-Arnés*, C. Sierra**, F. Tinahones*, A. Monzón***, M.J. López*,
N. Mazuecos****, F. Soriguer* and E. Valverde***
*
Endocrinology Service, **Gastroenterology and Infant Nutrition Unit, ***Pharmacy Service Laboratory,
***Hormone Laboratory, Carlos Haya Hospital Complex, Málaga, Spain
*
ABSTRACT. Pathological disruption of the intesti-
nal mucosa increases the paracellular pathway,
leading to an increase in the penetration of large
molecules. Since growth hormone (GH) has a troph-
ic intestinal effect, we used a double marker test
to enable examination of intestinal permeability,
which reflects the state of integrity of the intesti-
nal mucosa. We recruited 22 adult patients, mean
age 54±±1.1 years, with GH deficiency due to par-
tial or total hypopituitarism. None had received GH
treatment at any time, although they were all in op-
timized replacement therapy. A control group was
composed of ±9 healthy age-matched relatives. The
intestinal permeability test was performed with lac-
tulose (5 g) and mannitol (± g) after an oral load of
lose/mannitol ratio and the percentages of lactu-
lose and mannitol excreted were determined on a
5-h urine collection. There were no significant diffe-
rences between the patients and the control group
in the lactulose/mannitol ratio (0.087±0.059 vs
0.077±0.0ꢀ4, respectively) or in the urinary ex-
cretion percentages of lactulose (0.0ꢀ7±0.048ꢁ
vs 0.071±0.070ꢁ, respectively) or mannitol
(5.±27±1.2ꢀ9ꢁ vs 5.0ꢀ8±2.985ꢁ, respectively).
In conclusion, no increase in intestinal permeabi-
lity was detected in patients with GH deficiency,
so that in spite of the known trophic effects of
GH on the epithelial crypt cells, there was no in-
testinal hyperpermeability in these patients.
(J. Endocrinol. Invest. 24: 78-82, 200±)
©
±
00 ml of aqueous solution. The urinary lactu-
200±, Editrice Kurtis
INTRODUCTION
the crypts. The beneficial effect of GH on intestinal
growth has been described in rats after massive in-
testinal resection, demonstrating a marked trophic
effect on the intestinal mucosa (5).
Alterations in the physiological characteristics of the
intestinal mucosa sometimes occur, for example in
cases of prolonged intestinal rest even if the in-
testinal surface remains intact, as happens during
total parenteral nutrition (1), in cases of reduction of
the intestinal absorption surface area due to severe
intestinal resection (short bowel syndrome) (2), or
in situations of loss of intestinal integrity, as in vil-
lous atrophy (celiac disease) (3).
Little is known of the action of GH in the human
gastrointestinal tract, although it is possibly in-
volved in the local synthesis of IGF-I, which is ex-
pressed in the gastrointestinal tract (4), thereby in-
creasing autocrine or paracrine cell proliferation in
The intestinal mucosa in healthy subjects acts as a
defensive barrier preventing the passage of toxic
substances from the intestinal lumen to the blood-
stream (6). Urinary excretion of substances with dif-
ferent molecular weights and different forms of in-
testinal absorption, such as lactulose (molecular
weight 342 Da) or mannitol (molecular weight 182
Da), is used as a simple, non-invasive, and repro-
ducible test of intestinal permeability (IP), reflect-
ing the presence or absence of enteropathy (7). The
larger molecules, such as lactulose, use the para-
cellular route via the intercellular junction com-
plexes and the areas of extrusion, and the smaller
molecules, like mannitol, cross via transcellular
channels through the numerous aqueous pores lo-
cated on the cell membrane. The degree of urinary
excretion of both molecules changes according to
the osmolarity: the higher the osmolarity, the high-
er the degree of urinary excretion.
Key-words: GH deficiency, hypopituitarism, intestinal permeability, lac-
tulose, mannitol.
Correspondence: Dr. Juan García-Arnés, Servicio de Endocrinología,
Hospital Civil, Complejo Hospitalario “Carlos Haya”, Malaga, Spain.
E-mail: jgarnes@hch.sas.cica.es.
Accepted 16 June, 2000.
78

Intestinal permeability in GH deficiency
MATERIALS AND METHODS
Numerous studies (8, 9) demonstrated changes in
body composition with an increase in fat mass and
the hip-to-waist ratio, as well as a reduction in muscle
mass and extracellular water, in adult patients with
GH deficiency. Changes in lipid metabolism have al-
so been reported (10), which, together with cardiac
abnormalities (11), might explain the high level of car-
diovascular mortality. Likewise, a reduction in bone
density has been shown with a decrease in markers of
osteoblastic activity (12), and finally, psychological
disorders and a reduced quality of life have also been
described (13). Many of these conditions improve par-
tially or wholly after replacement therapy (9, 14), thus
demonstrating the multiple actions of GH on the or-
ganism. GH has accordingly been considered for use
in other pathologies such as severe catabolic states
and some forms of malnutrition, or to increase ath-
letic performance (15). To date, however, no studies
concerning the possible changes in trophism or IP
have been carried out in adults with GH deficiency.
A total of 22 patients, 15 men and 7 women, mean
age 54±13.3 years, with partial or total hypopitu-
itarism and GH deficiency were included in the study.
The hypopituitarism was due to several different pro-
cesses, including prolactinoma, Sheehan syndrome,
non-functioning pituitary tumor, parasellar menin-
gioma, empty sella turcica, cholesteatoma, cranio-
pharyngioma, cranial trauma and idiopathic causes
(Table 1). No patient had received GH treatment at
any time before testing and all had been in opti-
mized replacement therapy with L-thyroxine and hy-
drocortisone, plus testosterone in all the men or es-
trogen in the women younger than 45 years of age.
The cases with ADH deficiency were also being ad-
equately treated with desmopressin. Written in-
formed consent was obtained and the study was ap-
proved by the hospital ethics committee. An age-
matched control group was composed of 19 healthy
relatives of the patients, 13 men and 6 women.
Table 1 - Etiology of the hypopituitarism, duration in years and peak GH values after insulin-induced hypoglycemia, plus basal IGF-I in ng/ml
and IGFBP-3 values in μg/ml.
Case
Etiology
Duration
Peak GH
0.8
1.0
1.2
1.8
0.7
1.1
0.6
-
IGF-I
62
56
78
-
IGFBP-3
1.30
2.30
2.76
-
1
2
3
4
5
6
7
8
9
Prolactinoma
6
12
7
Sheehan syndrome
Non-functioning tumor
Prolactinoma
8
Parasellar meningioma
Empty sella turcica
Non-functioning tumor
Idiopathic
2
43
93
-
1.12
1.83
-
4
11
7
62
51
68
40
91
170
79
-
1.03
1.17
2.65
2.61
3.08
4.01
1.83
-
Cholesteatoma
10
17
3
0.5
0.8
0.9
2.2
1.0
0.8
0.8
1.7
1.0
0.7
1.0
0.7
0.9
0.5
10
11
12
13
14
15
16
17
18
19
20
21
22
Non-functioning tumor*
Craniopharyngioma*
Craniopharingioma
Non-functioning tumor
Prolactinoma
7
4
12
2
Non-functioning tumor
Empty sella turcica
Empty sella turcica
Non-functioning tumor
Empty sella turcica
Cranial trauma
8
-
-
2
115
23
33
79
19
90
2.84
1.33
1.54
3.21
0.73
3.93
6
11
11
19
2
Idiopathic
Prolactinoma
All cases of FSH, LH, TSH, ACTH deficiency receiving replacement therapy; *associated ADH deficiency being treated with desmopressin.
79

J. García-Arnés, C. Sierra, F. Tinahones, et al.
GH was measured by IRMA (Hybritech, sensitivity
Table 2 - Results of intestinal permeability in patients with GH
deficiency and a control group (mean±SꢀD. Ratio of urinary
lactulose/mannitol and urinary excretion (%D of lactulose and
mannitol.
<
0.5 ng/ml, inter- and intraassay coefficients of vari-
ation: 13% and 1.5%, respectively) before and af-
ter an insulin tolerance test (0.15 IU/kg iv) and mea-
sured at baseline and on reaching the maximum
peak after achieving hypoglycemia (plasma glucose
Patients
Controls
p value
0.3465
0.6938
Lactulose/Mannitol 0.087±0.059
0.077±0.064
0.073±0.070
<
2 nmol/l). GH deficit was defined as a value at
Lactulose %
Mannitol %
0.067±0.048
maximum peak less than 3 ng/ml. Serum IGF-I lev-
els were assayed basally by RIA (Nichols Institute
Diagnostics) after acid-ethanol extraction to avoid
interference by binding proteins. The inter- and in-
traassay coefficients of variation were 7% and 2.5%,
respectively. The normal values in our laboratory
for adults are 90-290 ng/ml. IGFBP-3 measured
basally by RIA (Nichols Institute Diagnostics). The
inter- and intra-assay coefficients of variation were
5.127±3.269 5.068± 2.985 0.9271
patient and control groups in the urinary lactu-
lose/mannitol ratio (0.087±0.059 vs 0.077±0.064,
respectively) or in the urinary excretion of lactulose
(0.067±0.048% vs 0.073±0.070%, respectively) or
mannitol (5.127±3.269% vs 5.068±2.985%, re-
spectively) (Table 2).
6
% and 4%, respectively. The normal values in our
laboratory for adults are 1.33-3.58 μg/ml.
After a period of at least 8 hours, an IP test was per-
formed by means of an oral loading solution. The
solution contained 5-g lactulose and 1-g mannitol
in an aqueous solution of 100 ml. A 5-h urine col-
lection was made and 0.5 ml thiomersal was added
to a 5 ml sample for conservation at -20 C. Measu-
rements were made by gas liquid chromatography
DISCUSSION
The mitogenic effect of GH on epithelial cells in the
duodenal crypts of hypophysectomized rats has
been demonstrated (16). On the other hand, hy-
pophysectomy in rats with an intact small bowel
causes mucosal hypoplasia with a reduction of en-
zymatic activity and a segmentary decrease in in-
testinal absorption (17). The pituitary hormones,
such as GH, can influence the adaptive response
to intestinal resection in rats (18). Challacombe et al.
(19) showed the trophic effect of GH on human
duodenal mucosa cultured in vitro.
Oral feeding is the main stimulus for the mainte-
nance of intestinal trophism, so that enteral nutri-
tion is preferable to parenteral nutrition. Different
nutrients have different stimulatory effects on in-
testinal trophism: disaccharides more than mono-
saccharides (20), long-chain triglycerides more than
medium chain (21), glutamine (22) zinc (23) and oth-
ers. Growth factors play an important role in in-
testinal trophism. Cellular proliferation and differ-
entiation is stimulated by the epidermal growth fac-
tor (22) and polyamines (24).
(
Perkin-Elmer 8410 gas Chromatograph) at an in-
jector temperature of 350 C and a detector tem-
perature of 350 C. The initial oven temperature was
1
50 C, the isotime 8 min and the temperature gra-
dient 15 C/min until reaching a final temperature
of 300 C. The nitrogen flow was 8 ml/min.
IP was expressed by the ratio of lactulose/mannitol
in urine, the excretion of lactulose and mannitol re-
flecting the state of paracellular and transcellular
penetration respectively. An isotonic solution was
used to ensure good clinical tolerance, and the fast
maintained for the whole study period (5 h).
Statistical analysis
The results are expressed as the mean±SD. The
Mann-Whitney test was used to compare means,
and p values <0.05 were considered significant.
Investigation of IP is an effective way of determining
the integrity of intestinal mucosa. Changes in IP cor-
relate with the degree of villous lesion, although they
have also been reported in patients being treated for
celiac disease who had a histologically normal jeju-
nal mucosa (25). The ratio of large molecules is
thought to be dependent on several factors such as:
features of the solution (content of both molecules
and osmolarity), gastric emptying, intestinal transit,
and renal clearance, apart from the functional integrity
of the intestinal mucosa.
RESULTS
In all subjects there was good tolerance to the ad-
ministration of the double marker. In the patient
group the lactulose/mannitol ratio ranged from
0
.029 to 0.273, the lactulose excretion from 0.001%
to 0.16% and mannitol excretion from 1.3% to
3.5%. In the control group the lactulose/mannitol
1
ratio ranged from 0.014 to 0.266, lactulose excre-
tion from 0.001% to 0.26% and mannitol excretion
from 1.1% to 13.2%.
No significant differences were found between the
The results (18, 26) vary according to the type of
80

Intestinal permeability in GH deficiency
solution, period of urine collection and fasting time;
obviously, the volume of the urine will vary and con-
sequently the percentage of excretion of both
molecules. However, the urinary lactulose/manni-
tol ratio will not change, which in fact defines the
state of IP. As well as others (27, 28), we maintained
the fasting period for the whole study period, there-
fore the collected volume of urine is less, and ob-
viously the urinary excretion of both molecules will
be lower.
In our study there were no differences in IP be-
tween the patients with GH deficiency and the con-
trol group. There was, therefore, no disruption in
the intestinal mucosa of patients with GH deficien-
cy, as demonstrated by the normal ratio of urinary
lactulose/mannitol. Neither did there appear to be
an increase in paracellular transport (normal per-
centage of urinary lactulose excretion) or a reduc-
tion in the absorptive surface (no significant differ-
ences in urinary mannitol compared to the control
group). The existence of intraluminal nutrients de-
rived from oral feeding is probably adequate for
maintenance of intestinal trophism in spite of the
presence of GH deficiency. In clinical practice the IP
test (differential absorption of sugar) may be used
to determine the presence or absence of en-
teropathy, defined as an alteration in the function-
al integrity of the small bowel (26). Although for
ethical reasons no intestinal biopsies were per-
formed, the existence of a normal intestinal villous
architecture can be supposed, especially if we con-
sider that minimal villous lesions are accompanied
by increased IP.
3. Kuitunen M., Savilahti E.
Gut permeability to human α-lactalbumin, β-lac-
toglobulin, mannitol, and lactulose in celiac
disease.
J. Ped. Gastroenterol. Nutr. 1996, 22: 197-204.
4.
5.
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Hansson H.A., Nilsson A., Isgaard J.
Immunohistochemical localization of insulin like
growth factor-1 in the adult rat.
Histochemistry 1988, 89: 403-410.
Shulman D.I., Hu C.S., Duckett G., Lavallee-Grey M.
Effects of short-term growth hormone therapy in rats
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J. Ped. Gastroenterol. Nutr. 1992, 14: 3-11.
Menzies I.S., Laker M.F., Pounder R., Bull J., Heyer
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Lancet 1979, 2: 1107-1109.
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Bjarnason I., Maxton D., Reynolds A.P., Catt S.,
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Scand. J. Gastroenterol. 1994, 29: 630-639.
8
9
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Clin. Endocrinol. (Oxf.) 1992, 37: 387-397.
Carrol P.V., Christ E.R., the Members of Growth Hor-
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Metabolism 1994, 47: 199-203.
Studies with double marker solutions may help to
clarify the role of IP in the pathophysiology of gas-
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phism. The normal results of the IP tests suggest
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oral feeding provides sufficient stimuli for ade-
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11. Merola B., Cittadini A., Colao A., Longobardi S.,
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1
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Clin. Endocrinol. (Oxf.) 1994, 40: 111-116.
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