Vestibular function in severe GH deficiency due to an inactivating mutation in the GH-releasing hormone receptor gene.

PURPOSE: Body balance involves the vestibular, visual, and proprioceptive systems. IGF-I is a GH-dependent key factor in the development and postnatal differentiation of the inner ear in mice and men, but its role in the vestibular function in adult humans is unknown. We have previously described a cohort of individuals with severe isolated GH deficiency (IGHD) caused by a mutation in the GHRH receptor (GHRHR) gene. These individuals complain of dizziness, exhibit mild sensorineural loss, but have normal postural balance, without increase in falls risk. The aim of this study was to evaluate their vestibular function. METHODS: We performed physical examination (clinical head impulse and Fukuda dynamic stepping test), oculomotor (saccadic eye movements, spontaneous, semi-spontaneous and opotokinetic nystagmus, and pendular tracking) and caloric stimulation (postcaloric reflex and ocular fixation index) tests, in 15 GH-naïve IGHD (seven males) and 15 controls (five males). RESULTS: IGHD subjects showed lower height and weight, with similar BMI to controls, and higher number of individuals with abnormal clinical head impulse test and abnormal oculomotor tests, namely the saccadic movements and the spontaneous nystagmus. There was a nonsignificant trend in abnormalities in the Fukuda stepping test and postcaloric reflex test. CONCLUSIONS: Adult untreated IGHD individuals have higher prevalence of moderate peripheral vestibular impairment, and of abnormal vestibular-ocular reflex.

Walking and postural balance in adults with severe short stature due to isolated GH deficiency.

OBJECTIVES: Walking and postural balance are extremely important to obtain food and to work. Both are critical for quality of life and ability to survive. While walking reflects musculoskeletal and cardiopulmonary systems, postural balance depends on body size, muscle tone, visual, vestibular and nervous systems. Since GH and IGF-I act on all these systems, we decided to study those parameters in a cohort of individuals with severe short stature due to untreated isolated GH deficiency (IGHD) caused by a mutation in the GHRH receptor gene. These IGHD subjects, despite reduction in muscle mass, are very active and have normal longevity. METHODS: In a cross-sectional study, we assessed walking (by a 6-min walk test), postural balance (by force platform) and fall risk (by the 'Timed Up and Go' test) in 31 IGHD and 40 matched health controls. RESULTS: The percentage of the walked distance measured in relation to the predicted one was similar in groups, but higher in IGHD, when corrected by the leg length. Absolute postural balance data showed similar velocity of unipodal support in the two groups, and better values, with open and closed eyes and unipodal support, in IGHD, but these differences became non-significant when corrected for height and lower-limb length. The time in 'Timed Up and Go' test was higher in IGHD cohort, but still below the cut-off value for fall risk. CONCLUSION: IGHD subjects exhibit satisfactory walking and postural balance, without increase in fall risk.

Adult individuals with congenital, untreated, severe isolated growth hormone deficiency have satisfactory muscular function.

PURPOSE: While growth hormone (GH) and the insulin-like growth factor type I (IGF-I) are known to exert synergistic actions on muscle anabolism, the consequences of prolonged GH deficiency (GHD) on muscle function have not been well defined. We have previously described a large cohort of subjects with isolated GHD (IGHD) caused by a mutation in the GH-releasing hormone receptor gene, with low serum levels of GH and IGF-I. The aim of this study was to assess muscular function in these IGHD subjects. METHODS: A total of 31 GH-naïve IGHD (16 males) and 40 control (20 males) subjects, matched by age and degree of daily physical activity, were enrolled. Fat free mass was measured by bioelectrical impedance; muscle strength by dynamometry of handgrip, trunk extension, and knee extension; myoelectric activity and muscle fatigue by fractal dimension; conduction velocity in vastus medialis, rectus femoris, and vastus lateralis muscles by surface electromyography. RESULTS: The IGHD group showed higher knee extension strength both when corrected for weight and fat free mass, and higher handgrip and trunk extension strength corrected by fat free mass. They also exhibit higher conduction velocity of the muscles vastus medialis, rectus femoris, and vastus lateralis, but lower free fat mass and myoelectric activity of the vastus medialis, rectus femoris and vastus lateralis. There were no differences between the two groups in fractal dimension in all studied muscles. CONCLUSION: Individuals with untreated IGHD have better muscle strength parameters adjusted for weight and fat free mass than controls. They also exhibit greater peripheral resistance to fatigue, demonstrating satisfactory muscle function.

Older individuals heterozygous for a growth hormone-releasing hormone receptor gene mutation are shorter than normal subjects.

Growth hormone (GH)-releasing hormone (GHRH) is the most important stimulus for GH secretion by the pituitary gland. Subjects homozygous for GHRH receptor (GHRHR) gene (GHRHR) inactivating mutations have severe GH deficiency, resulting in severe short stature if not treated. We previously reported that young adults heterozygous for the c.57+1G>A null GHRHR mutation (MUT/N) have reduced weight and body mass index (BMI) but normal stature. Here we have studied whether older MUT/N have an additional phenotype. In a cross-sectional study, we measured height, weight and blood pressure, and calculated BMI in two groups (young, 20-40 years of age) and old (60-80 years) of individuals heterozygous for the same GHRHR mutation, and compared with a large number of individuals of normal genotype residing in the same geographical area. Standard deviation score (SDS) of weight was lower, and BMI had a trend toward reduction in young heterozygous compared with young normals, without significant difference in stature. Conversely, SDS of height was lower in older heterozygous individuals than in controls, corresponding to a reduction of 4.2 cm. These data show a reduced stature in older subjects heterozygous for the c.57+1G>A GHRHR mutation, indicating different effects of heterozygosis through lifespan.

Lifetime, untreated isolated GH deficiency due to a GH-releasing hormone receptor mutation has beneficial consequences on bone status in older individuals, and does not influence their abdominal aorta calcification.

The GH/IGF-I axis has essential roles in regulating bone and vascular status. The age-related decrease in GH secretion ("somatopause") may contribute to osteoporosis and atherosclerosis, commonly observed in the elderly. Adult-onset GH deficiency (GHD) has been reported to be associated with reduced bone mineral density (BMD), increased risk of fractures, and premature atherosclerosis. We have shown the young adult individuals with isolated GHD (IGHD) due to a homozygous for the c.57+1G>A GHRH receptor gene mutation have normal volumetric BMD (vBMD), and not develop premature atherosclerosis, despite adverse risk factor profile. However, the bone and vascular impact of lifetime GHD on the aging process remains unknown. We studied a group of ten older IGHD subjects (≥60 years) homozygous for the mutation, comparing them with 20 age- and gender-matched controls (CO). Areal BMD was measured, and vBMD was calculated at the lumbar spine and total hip. Vertebral fractures and abdominal aortic calcifications (expressed as calcium score) were also assessed. Areal BMD was lower in IGHD, but vBMD was similar in the two groups. The percent of fractured individuals was similar, but the mean number of fractures per individual was lower in IGHD than CO. Calcium score was similar in the two groups. A positive correlation was found between calcium score and number of fractures. Untreated lifetime IGHD has beneficial consequences on bone status and does not have a deleterious effect on abdominal aorta calcification.

Isolated GH deficiency due to a GHRH receptor mutation causes hip joint problems and genu valgum, and reduces size but not density of trabecular and mixed bone.

CONTEXT: The GH/IGF-I axis is important for bone growth, but its effects on joint function are not completely understood. Adult-onset GH-deficient individuals have often reduced bone mineral density (BMD). However, there are limited data on BMD in adult patients with untreated congenital isolated GH-deficient (IGHD). We have shown that adult IGHD individuals from the Itabaianinha, homozygous for the c.57+1G>A GHRHR mutation, have reduced bone stiffness, but BMD and joint status in this cohort are unknown. OBJECTIVE: The goal is to study BMD, joint function, and osteoarthritis score in previously untreated IGHD adults harboring the c.57+1G>A GHRHR mutation. DESIGN: This is a cross-sectional study. METHODS: Areal BMD by dual-energy X-ray absorptiometry was measured in 25 IGHD and 23 controls (CO). Volumetric BMD (vBMD) was calculated at the lumbar spine and total hip. Joint function was assessed by goniometry of elbow, hips, and knees. X-rays were used to measure the anatomic axis of knee and the severity of osteoarthritis, using a classification for osteophytes (OP) and joint space narrowing (JSN). RESULTS: Genu valgum was more prevalent in IGHD than CO. The osteoarthritis knees OP score was similar in both groups, and knees JSN score showed a trend to be higher in IGHD. The hips OP score and JSN score were higher in IGHD. Areal BMD was lower in IGHD than CO, but vBMD was similar in the two groups. Range of motion was similar in elbow, knee, and hip in IGHD and CO. CONCLUSIONS: Untreated congenital IGHD due to a GHRHR mutation causes hip joint problems and genu valgum, without apparent clinical significance, reduces bone size, but does not reduce vBMD of the lumbar spine and hip.

Longevity in untreated congenital growth hormone deficiency due to a homozygous mutation in the GHRH receptor gene.

CONTEXT: Reduced longevity observed in hypopituitarism has been attributed to GH deficiency (GHD). It is, however, unclear whether GHD or other confounding factors cause this early mortality. OBJECTIVE: The aim was to study longevity in subjects from a large kindred with untreated, lifetime isolated GHD (IGHD) due to a homozygous mutation in the GHRH receptor gene and in heterozygous carriers of the mutation. DESIGN, SETTING, AND PARTICIPANTS: We carried out a retrospective cohort study on three groups. We first compared mortality risk of 65 IGHD individuals and their 128 unaffected siblings from 34 families. We then compared mean age of death of the IGHD to the general population. A transversal study was carried out to compare the rate of heterozygosity for the mutation in two groups of young (20-40 yr old) and old (60-80 yr old) normal-appearing subjects from the same county. MAIN OUTCOME MEASURE: We measured longevity. RESULTS: The risk of death of IGHD subjects was not different from their siblings. Life span in IGHD individuals was shorter than the general population. When stratified by sex, this difference persisted only in females, due to a high frequency of IGHD deaths in females aged 4-20. There was no significant difference in life span between IGHD subjects and siblings or the general population when analyzing subjects who reached age 20. The prevalence of heterozygosity did not differ in young and old groups, suggesting no survival advantage or disadvantage. CONCLUSIONS: In a selected genetic background, lifelong untreated IGHD does not affect longevity.

Consequences of lifetime isolated growth hormone (GH) deficiency and effects of short-term GH treatment on bone in adults with a mutation in the GHRH-receptor gene.

OBJECTIVE: Growth hormone (GH) influences bone mass maintenance. However, the consequences of lifetime isolated GH deficiency (IGHD) on bone are not well established. We assessed the bone status and the effect of 6 months of GH replacement in GH-naive adults with IGHD due to a homozygous mutation of the GH-releasing hormone (GHRH)-receptor gene (GHRHR). PATIENTS AND METHODS: We studied 20 individuals (10 men) with IGHD at baseline, after 6 months of depot GH treatment, and 6 and 12 months after discontinuation of GH. Quantitative ultrasound (QUS) of the heel was performed and serum osteocalcin (OC) and C-terminal cross-linking telopeptide of type I collagen (ICTP) were measured. QUS was also performed at baseline and 12 months later in a group of 20 normal control individuals (CO), who did not receive GH treatment. RESULTS: At baseline, the IGHD group had a lower T-score on QUS than CO (-1.15 +/- 0.9 vs.-0.07 +/- 0.9, P < 0.001). GH treatment improved this parameter, with improvement persisting for 12 months post-treatment (T-score for IGHD = -0.59 +/- 0.9, P < 0.05). GH also caused an increase in serum OC (baseline vs. pGH, P < 0.001) and ICTP (baseline vs. pGH, P < 0.01). The increase in OC was more marked during treatment and its reduction was slower after GH discontinuation than in ICTP. CONCLUSIONS: These data suggest that lifetime severe IGHD is associated with significant reduction in QUS parameters, which are partially reversed by short-term depot GH treatment. The treatment induces a biochemical pattern of bone anabolism that persists for at least 6 months after treatment discontinuation.