Long-term effects of growth hormone on body composition and metabolic parameters in girls with Turner syndrome

Abstract

Introduction

Patients with Turner syndrome (TS) are at increased risk of metabolic complications, partly as a consequence of truncal obesity, which can already appear in childhood. Growth hormone (GH) therapy is widely used in this population and is known to exert a beneficial effect on body composition (BC). The study aims to evaluate the impact of GH therapy on BC and explore associations between BC parameters and components of metabolic syndrome in girls with TS during a 5-year follow-up.

Material and methods

Twenty-one TS patients were enrolled. Auxological, BC, and biochemical parameters were assessed at baseline (V1), after 3 years (V3), and after 5 years (V5) of GH therapy. Results were available for 21, 20, and 13 patients, respectively. Biochemical phenotypes were determined using carbohydrate and lipid parameters.

Results

The only BC parameter that significantly increased during GH therapy was fat-free mass (FFM). Along with rising insulin-like growth factor 1 levels, fasting and postprandial insulin concentrations, as well as insulin resistance, increased during treatment. Total cholesterol decreased, although without significant changes in its fractions. No significant correlations were found between BC parameters, glucose, and total cholesterol during the GH 5-year follow-up.

Conclusions

Growth hormone therapy exerts a beneficial effect on BC in girls with TS, reflected by an increase in FFM. However, carbohydrate metabolism should be closely monitored, in line with national program requirements, due to the increased insulin resistance during GH therapy. Lifestyle recommendations promoting healthy behaviors should be provided to all patients with TS.

Introduction

Women with Turner syndrome (TS) are more frequently obese, with a central distribution of adiposity [1]. Adult TS patients have lower total lean body mass, while fat mass is elevated [2]. In girls with TS, higher waist circumference and a thicker layer of subcutaneous adipose tissue are also observed [3]. Turner syndrome is characterized by the frequent occurrence of carbohydrate and lipid metabolism disorders. Many studies indicate that metabolic disorders are more common in female TS patients than in the general population and are noticeable already in childhood [1]. Compared to the general population, women with TS have a two-fold higher risk of developing type 2 diabetes and a 4.5-fold higher risk of developing impaired glucose tolerance [4]. Girls with TS are also more likely than the general population to have impaired glucose tolerance and insulin resistance [5] as well as reduced insulin sensitivity compared to age-matched controls [6]. The majority of girls with TS are treated with growth hormone (GH). Our previous study demonstrated impaired development of insulin resistance and carbohydrate metabolism during GH therapy in girls with TS [7]. On the other hand, a beneficial effect on body composition (BC) has been reported [8].

As obesity can lead to the development of cardiovascular diseases (CVD) and, in consequence, to increased mortality, the improvement of BC may reduce the risk of CVD in TS patients (8). This is particularly important because congenital heart diseases and components of metabolic syndrome lead to shorter life expectancy in adult TS patients [9].

The study aimed to investigate the effect of GH therapy on BC and establish the relationship between BC parameters and metabolic syndrome components in girls with TS during a 5-year follow-up.

Material and methods

In this prospective study, 21 patients with TS, confirmed by karyotyping with routine G-banding (according to the recommendations of the American College of Medical Genetics), who started GH therapy between 2007 and 2019 at the Department of Pediatrics and Pediatric Endocrinology with a dose of 47–66 µg/kg/day according to the Polish Drug Program, were enrolled. The criteria for inclusion into the study group were: TS, age from 5 to 18 years, the onset and continuation of GH therapy at our center, and lack of coexisting diseases that could temporarily affect test results (severe infections). Exclusion criteria were a lack of consent of the legal guardian and/or the patient to participate in the study, and/or taking medications that could temporarily affect the measured and laboratory parameters.

For each patient, auxological, BC, and biochemical parameters were measured before starting GH treatment. Then, clinical and biochemical parameters were monitored every 3–6 months according to the protocol of the Polish Drug Program until the end of GH therapy. Data before the start of GH therapy (V0) were obtained from 21 subjects, then after the first year (V1) of GH therapy in 21 patients, the third (V3) year in 20 patients, and the fifth (V5) year of GH therapy in 13 patients (Figure 1).

Figure 1.

The course of the study

BF – body fat; BMI – body mass index; FFM – fat-free mass; fT4 – free thyroxine; HC – hip circumference; HOMA-IR – index of insulin resistance; hSDS – height standard deviation; IGF-1 – insulin-like growth factor 1; MM – muscle mass; WC – waist circumference; WHR – ratio of waist circumference to hip circumference; WHtR – ratio of waist circumference to height; TBW – total body water; TSH – thyroid-stimulating hormone

The anthropometric characterization was based on weight and height measurements, along with body mass index (BMI) calculation, using the standard formula of weight (kg) divided by height (m) squared, and evaluated on the chart for healthy girls [6].

Weight was measured with a TANITA MC-980 device with a precision of 100 g, and height with a Harpenden stadiometer with a graduation of 0.1 cm. Height was expressed as standardized values (height standard deviation score – hSDS) and was calculated using the following formula: hSDS = child’s height − height for 50^th percentile/0.5 × height 50^th percentile − height 3^rd percentile. Based on the age, sex, BMI, and the appropriate reference standard, the BMI Z-score was calculated using the international (International Obesity Task Force; IOTF) body mass index (BMI) cut-offs [10]. Tanner staging was used for puberty assessment [11].

The measurements of waist and hip circumference were obtained in an upright position, midway between the lowest rib margin and the iliac crest, and at the widest point of the hips, respectively, to the nearest 0.1 cm using an inelastic tape. The waist-to-height ratio (WHtR) and waist-hip ratio (WHR) were calculated by dividing both values.

The body composition was measured using a TANITA MC-980 BC analyzer, which is intended for professional use in hospitals and medical facilities, as well as universities for scientific research. The current flows at six frequencies (1 kHz/5 kHz/50 kHz/250 kHz/500 kHz/1000 kHz), which maximizes measurement accuracy. The following parameters were taken into account: body weight in kilograms, body fat (BF) mass in percentages, muscle mass (MM) in kilograms, total body water (TBW) content in kilograms, and free-fat mass (FFM) in kilograms.

Morning fasting venous blood samples were collected to measure the concentrations of total cholesterol (TCh), HDL cholesterol (HDL-C), and triglycerides (TG). TCh, HDL-C, and TG levels were analyzed enzymatically (Beckman Coulter, Brea, CA). An oral glucose load test of 1.75 g/kg was performed, with the determination of glucose and insulin levels at two time points: 0' and 120'. An enzymatic test (hexokinase method) was used for the quantitative determination of glucose (Beckman Coulter). Insulin was determined using a chemiluminescence immunoassay on an IMMULITE 2000 analyzer. Insulin resistance (IR) was measured using the HOMA index (HOMA-IR), calculated as fasting glucose [mg/dl] × fasting insulin [µUI/ml] /405 [12]. The fasting insulin [mIU/l]-to-glucose [mg/dl] ratio was also used as an index of IR, with a ratio > 0.3 considered indicative of IR [13].

Additionally, TSH (thyroid-stimulating hormone), free thyroxine (fT4), and insulin-like growth factor 1 (IGF-1) were also determined. Serum concentrations of fT4 and TSH were measured with a chemiluminescent immunometric assay (IMMULITE 2000 Free T4 and IMMULITE 2000 Third Generation TSH, respectively; Siemens), and IGF concentration was measured by solid-phase enzyme-labeled chemiluminescent immunometric assays (IMMULITE, DPC).

Statistical analysis

Data processing and statistical analyses were performed using STATISTICA v.13 (license No. JPZ804I382130ARCN10J) software and Microsoft Excel (2013). The distribution of quantitative values was evaluated according to the Shapiro-Wilk test.

Given the non-normal distribution of quantitative variables, their descriptive statistics were presented as the median (Me) and lower (Lq) and upper (Uq) quartiles. Comparative analysis of quantitative indicators in three or more groups was performed using the Kruskal–Wallis H test, which was considered significant at p < 0.05.

Comparisons of groups were performed using the Mann–Whitney U test with Bonferroni correction to assess the level of statistical significance.

The Pearson chi-square test (χ²) was used to analyze frequencies. To evaluate the possible associations between the studied data, Spearman correlation coefficients were determined. The significance of the differences between the values was considered significant at p < 0.05.

Bioethical standards

The study followed the ethical standards of the Declaration of Helsinki of 1975, as revised in 2013, as well as national laws. Patient safety rules and the ethical standards and procedures for research on human beings were followed. The idea of evaluating metabolic parameters and body mass composition in girls with TS was approved by the Ethics Committee of the Medical University of Silesia (resolution number NN-013-96/I/03 and KNW/0022/KB1/162/15/16).

Results

The study group consisted of 21 TS patients with median age 10 ±2.8 years. None of the patients had hypertension at the start of therapy. Of the 13 patients continuing therapy after 5 years (mean age 14.7 ±2.8 years), arterial hypertension was observed in 1 girl.

The only BC parameter that increased significantly during GH therapy, apart from weight and height, was FFM. The details related to clinical and laboratory parameters are demonstrated in Tables I and II.

Table I.

Dynamics of changes in anthropometrical parameters in patients with TS depending on GH therapy duration (Lq; Uq)

Auxological and body composition components	Duration of GH therapy				Kruskal-Wallis test (H) p	p Mann-Whitney U-test
	To 3 years V3 (n= 20)		To 5 years V5 (n= 13)
Weight, kg	28.40	30.60	35.20	43.10	H = 8.25	pV0-V1= 0.634
	(23.70; 38.00)	(24.10; 38.80)	(26.15; 45.75)	(32.90; 45.70)	p= 0.041*	pV0-V3= 0.187
						pV0-V5= 0.017*
Height, cm	126.0	128.2	136.1	144.2	H = 11.34	pV0-V1= 0.352
	(111.8; 135.6)	(117.5; 141.5)	(124.8; 146.5)	(137.2; 149.0)	p= 0.01*	pV0-V3= 0.065
						pV0-V5= 0.003*
hSDS	–2.39	–2.36	–2.35	–1.77	H = 4.68	pV0-V1= 0.409
	(3.63; –2.05)	(3.45; –1.83)	(–3.32; –1.64)	(–3.21; –1.54)	p= 0.196	pV0-V3= 0.104
						pV0-V5= 0.052
BMI, kg/m2	18.01	18.38	18.89	19.84	H = 1.22	pV0-V1= 0.896
	(16.49; 21.58)	(16.38; 20.51)	(16.26; 21.58)	(18.02; 20.45)	p= 0.748	pV0-V3= 0.825
						pV0-V5= 0.394
BMI Z–score	0.49	0.59	0.08	0.38	H = 0.041	pV0-V1= 0.776
	(–0.69; 1.39)	(–0.62; 1.01)	(–0.370; 1.09)	(–0.21; 1.09)	p= 0.997	pV0-V3= 0.817
						pV0-V5= 0.997
WC, cm	60.0	61.0	62.0	62.5	H = 2.01	pV0-V1= 0.542
	(58.0; 61.5)	(58.2; 66.5)	(58.0; 67.0)	(58.5; 69.2)	p= 0.569	pV0-V3= 0.573
						pV0-V5= 0.453
HC, cm	70.0	71.0	73.5	73.0	H = 1.17	pV0-V1= 0.352
	(69.5; 74.0)	(70.0; 79.5)	(70.0; 79.0)	(69.0; 81.5)	p= 0.759	pV0-V3= 0.426
						pV0-V5= 0.474
WHR	0.85	0.84	0.84	0.85	H = 0.447	pV0-V1= 0.838
	(0.83; 0.86)	(0.81; 0.88)	(0.83; 0.86)	(0.83; 0.88)	p= 0.930	pV0-V3= 0.815
						pV0-V5= 0.639
WHtR	0.50	0.47	0.47	0.45	H = 3.21	pV0-V1= 0.257
	(0.46; 0.52)	(0.35; 0.48)	(0.45; 0.51)	(0.44; 0.47)	p= 0.360	pV0-V3= 0.410
						pV0-V5= 0.217
BF, %	25.40	20.00	22.50	24.30	H = 4.01	pV0-V1= 0.088
	(20.50; 28.70)	(18.20; 23.20)	(20.45; 25.60)	(21.05; 25.75)	p= 0.261	pV0-V3= 0.345
						pV0-V5= 0.648
MM, kg	20.40	25.00	25.20	24.70	H = 3.94	pV0-V1= 0.136
	(15.60; 27.23)	(21.00; 28.90)	(19.65; 26.27)	(22.42; 29.92)	p= 0.267	pV0-V3= 0.238
						pV0-V5= 0.102
TBW, kg	15.60	18.00	19.40	19.05	H = 5.63	pV0-V1= 0.081
	(11.90; 17.95)	(16.30; 22.30)	(15.25; 20.22)	(17.35; 23.07)	p= 0.130	pV0-V3= 0.108
						pV0-V5= 0.055
FFM, kg	21.30	24.60	26.50	26.05	H = 8.20	pV0-V1= 0.057
	(16.40; 24.55)	(22.20; 30.50)	(20.77; 27.67)	(23.67; 31.55)	p= 0.042*	pV0-V3= 0.086
						pV0-V5= 0.038*

^*p < 0.05 – statistically significant difference

hSDS – height standard deviation; BMI – body mass index; BMI Z-score – body mass index Z-score; WC – waist circumference; HC – hip circumference; WHR – ratio of waist circumference to hip circumference; WHtR – ratio of waist circumference to height; BF – body fat; MM – muscle mass; TBW – total body water; FFM – fat-free mass

Changes in carbohydrate and lipid parameters in the course of GH therapy included an increase in insulin and insulin 120' levels, as well as an increase in insulin resistance during treatment, without statistically significant differences in glucose concentration during GH treatment. Total cholesterol decreased during therapy, with no statistically significant changes in its individual fractions. An increase in IGF-1 concentration was also observed during treatment (Table II). The correlation between BC characteristics and metabolic parameters is presented in Figure 2. Apart from the clear correlation between BC and duration of therapy, no significant correlations were found between BC, glucose, and cholesterol levels during the GH 5-year follow-up.

Table II.

Dynamics of carbohydrate and lipid parameters in patients with TS depending on GH therapy duration (Lq; Uq)

Variables	Duration of GH therapy				Kruskal-Wallis test (H) p	p Mann-Whitney U-test
	Therapy onset V0 (n = 21)	To 1 year V1 (n = 21)	To 3 years V3 (n= 20)	To 5 years V5 (n= 13)
Glucose 0', mg/dl	90.00 (84.50; 96.25)	95.00 (84.00; 99.00)	92.50 (87.00; 96.00)	95.00 (88.00; 101.00)	H = 2.77 p= 0.428	pV0-V1 =0.354 pV0-V3 =0.745 pV0-V5 =0.113
Glucose 120', mg/dl	114.5 (101.5; 122.0)	122.0 (102.0; 130.5)	120.5 (107.5; 131.0)	114.0 (104.0; 128.0)	H = 1.32 p= 0.725	pV0-V1 =0.375 pV0-V3 =0.291 pV0-V5 =0.518
Insulin 0', UI/I	3.00 (1.50; 5.85)	9.70 (6.10; 13.90)	10.60 (8.50; 13.50)	14.10 (9.90; 16.42)	H = 24.94 p= 0.000*	pV0-V1 =0.003* pV0-V3 =0.000* pV0-V5 =0.000*
Insulin 120', UI/I	30.70 (19.95; 57.93)	50.10 (32.35; 75.85)	67.65 (37.17; 88.80)	69.70 (58.40; 86.40)	H = 11.13 p= 0.011*	pV0-V1 =0.089 pV0-V3 =0.019* pV0-V5 =0.011*
Insulin/ glucose	0.035 (0.019; 0.063)	0.110 (0.070; 0.140)	0.125 (0.080; 0.150)	0.140 (0.090; 0.160)	H = 24.18 p= 0.000*	pV0-V1 =0.002* pV0-V3 =0.000* pV0-V5 =0.000*
HOMA-IR	0.66 (0.32; 1.46)	2.04 (1.33; 3.52)	2.29 (1.84; 3.08)	3.22 (2.41; 4.05)	H = 24.11 p= 0.000*	pV0-V1 =0.003* pV0-V3 =0.000* pV0-V5 =0.000*
HbA1c, %	5.30 (5.30; 5.65)	5.40 (5.10; 5.60)	5.40 (5.05; 5.50)	5.30 (5.00; 5.45)	H = 0.47 p= 0.926	pV0-V1 =0.859 pV0-V3 =0.741 pV0-V5 =0.696
TCh, mg/dl	178.0 (166.25; 191.75)	175.0 (165.0; 192.7)	160.0 (148.5; 168.5)	155.0 (139.0; 177.0)	H = 13.32 p= 0.003*	pV0-V1 =0.555 pV0-V3 =0.003* pV0-V5 =0.009*
HDL-C, mg/dl	60.30 (55.80; 69.58)	59.45 (54.67; 65.92)	56.60 (53.75; 64.55)	56.90 (53.20; 61.60)	H = 2.69 p= 0.441	pV0-V1 =0.575 pV0-V3 =0.302 pV0-V5 =0.169
TG, mg/dl	74.50 (69.25; 103.75)	87.50 (66.75; 103.25)	88.00 (66.00; 108.75)	97.00 (82.00; 108.00)	H = 0.98 p= 0.806	pV0-V1 =0.599 pV0-V3 =0.611 pV0-V5 =0.395
non-HDL-C, mg/dl	114.00 (105.00; 142.00)	108.00 (100.00; 144.00)	108.00 (89.00; 124.00)	94.00 (81.00; 124.00)	H = 5.40 p= 0.145	pV0-V1 =0.740 pV0-V3 =0.079 pV0-V5 =0.166
fT4, ng/dl	1.38 (1.25; 1.51)	1.29 (1.11; 1.51)	1.30 (1.22; 1.41)	1.37 (1.27; 1.49)	H = 2.24 p= 0.523	pV0-V1 =0.935 pV0-V3 =0.223 pV0-V5 =0.736
TSH, μIU/ml	2.70 (1.78; 3.53)	2.68 (1.76; 3.49)	3.20 (2.63; 3.93)	2.20 (1.63; 3.30)	H = 2.37 p= 0.498	pV0-V1 =0.767 pV0-V3 =0.273 pV0-V5 =0.619
IGF-1, ng/ml	185.00	514.00	559.00	616.00	H = 27.48	pV0-V1= 0.000*
	(122.00; 270.75)	(380.50; 560.00)	(452.00; 707.50)	(448.00; 827.00)	p= 0.000*	pV0-V3= 0.000*
						pV0-V5= 0.000*

^*p < 0.05 – statistically significant difference.

HOMA-IR – index of insulin resistance; HbA1c – glycated hemoglobin; TC – total cholesterol; HDL-C – high-density lipoprotein cholesterol; TG – triglycerides; fT4 – free T4; TSH – thyroid-stimulating hormone; IGF-1 – insulin-like growth factor 1

Figure 2.

Correlation between body composition characteristics and metabolic parameters (heat map)

BF – body fat; FFM – fat-free mass; HC – hip circumference; HDL – high-density lipoprotein; MM – muscle mass; WC – waist circumference; TBW – total body water; Tch – total cholesterol; TG – triglicerydes

Pubertal changes were associated with key markers of BC, such as MM and FFM (p = 0.001).

Discussion

Patients treated with GH, while achieving accelerated growth and attaining an appropriate final height, gain beneficial effects on BC [14–16]. The same effect was observed in TS patients. Wooten et al. reported that abdominal adiposity was significantly lower in GH-treated vs. untreated TS girls, with an increase in the volume of MM and improvement of the proportion of MM to BF in treated girls. The study also revealed that effects were independent of estrogen exposure and were still observed in girls who finished GH treatment at least one year after the end of therapy [17]. Research by Polish authors on a group of TS patients after GH treatment vs. untreated patients revealed that a decrease in BF persists for several years after finishing GH treatment [18], which confirms the beneficial effect of the therapy.

It is known that inadequate BC is a predictor of cardiovascular risk, including TS patients [16]. Therefore, it seems that the effect of GH treatment has a protective effect in the context of cardiovascular diseases. However, it should not be forgotten that although GH therapy is associated with favorable changes in body composition, it is also connected with relative impairment of glucose tolerance and insulin sensitivity [19]. Our study revealed an increase in insulin, insulin 120', as well as insulin resistance. These are expected effects of GH treatment, especially since we use supra-substitution doses of GH in patients with TS. Thus, glucose metabolism should be monitored carefully during long-term GH treatment in these patients.

We also observed a decrease in TCh concentration during therapy. Individual lipid fractions did not show statistically significant changes. Similarly to our previous study with a 10-year follow-up, we did not observe a statistically significant difference in the serum triglycerides and HDL-C levels during GH therapy [7]. Bannink et al. revealed that TCh, LDL, and HDL increased after GH treatment discontinuation compared to 6 months after GH treatment. The atherogenic index remained constant, though lower than in controls; hence, GH therapy in girls with TS seems to have beneficial effects on serum lipids, visible even a few years after discontinuation of GH therapy [20].

In our study, no significant correlations were found between BC parameters, glucose, and TCh during the GH 5-year follow-up. This study may be limited by the small number of participants, potentially affecting the generalizability of the findings to the larger TS population. This limitation might reduce the statistical power and precision of the results. Variability in age during inclusion in the study and pubertal status among participants may also add some confounding variables.

The strength of our study is that it is a long-term prospective observation in patients with a rare disease carried out at one center, following a uniform protocol.

In addition to the clear effect of GH on the growth of treated patients, GH therapy also seems to be important in the context of cardiometabolic disturbances. Its positive influence is visible in the context of BC. However, parameters of carbohydrate metabolism should be monitored due to the increase in insulin resistance during GH therapy. Additionally, exercise should be promoted as a general component of a healthy lifestyle. Current recommendations for children with TS include at least 60 minutes of daily moderate to vigorous activities [21], especially as they have lower total lean body mass, and their VO₂max and physical activity levels are significantly lower compared to controls [2]. At our center, there is also good cooperation with a dietitian and a psychologist to strongly emphasize the importance of lifestyle.

Conflict of interest

non declared.

Funding

none.

Ethics approval

The study was approved by Ethics Committee of the Medical University of Silesia, Katowice, Poland (approval No.: NN-013-96/I/03 and KNW/0022/KB1/162/15/16).

Partial results were reported as an abstract at the 61st Annual European Society of Paediatric Endocrinology (ESPE) Meeting held on 21–23 September 2023, The Hague, Netherlands.