Saline solution will be administered for three months subcutaneously.

The Clinical Global Impression - Severity scale (CGI-S) is a 7-point scale that requires the clinician to rate the severity of the patient's illness at the time of assessment, relative to the clinician's past experience with patients who have the same diagnosis. Considering total clinical experience, a patient is assessed on severity of mental illness at the time of rating 1, normal, not at all ill; 2, borderline mentally ill; 3, mildly ill; 4, moderately ill; 5, markedly ill; 6, severely ill; or 7, extremely ill.

The Clinical Global Impression - Improvement scale (CGI-I) is a 7 point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of the intervention. and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

21 question tool, about caregiver strain, where each question uses a Likert scale where 1 is "Not at all" and 5 is "Very much." The full scale ranges from 21-105, where higher scores indicate more severe strain.

The SP is a standardized parent-completed questionnaire that assesses sensory processing and its impact on the functioning of children ages 3-10 yr. The 125 items represent behaviors that can be interpreted as responses to sensory experiences. The parent rates the observed frequency of these behaviors on a 5-point Likert scale (ranging from 1 always to 5 never). The tool consists of 14 sections, listed below, that refer to sensory processing, modulation, and behavioral and emotional responses. Subscale scores are listed below.

Each section's raw score is compared with a threshold value to determine a category of performance: typical performance, probable difference (1 standard deviation below the mean), and definite difference (2 standard deviations below the mean). A lower raw score means a greater difference.

The Short Sensory Profile is a caregiver report measure consisting of 38 items, each scored on a 1-point (always) to 5-point (never) Likert scale.

SSP Subscales Tactile Sensitivity (7 to 35) Taste/Smell Sensitivity (4 to 20), Movement Sensitivity (3 to 15), Under-Responsive/Seek Sensation (7 to 35) , Auditory Filtering (6 to 30), Low Energy/Weak (6 to 30), Visual/Auditory Sensitivity (5 to 25), with total scale from (38 to 190)

Lower scores indicate more sensory alterations.

Participants who have pathogenic deletions or sequence variants of the SHANK3 gene.

Insulin-Like Growth Factor-1 (IGF-1) and then placebo administered for 3 months with a four-week washout period in between. IGF-1 will be administered for 3 months subcutaneously.

12 weeks in each treatment arm (placebo and then IGF-1), separated by a 4-week wash-out phase

Total of all reporting groups

16 items on ABC-SW subscale, Each item is scored as 0 (never a problem), 1 (slight problem), 2 (moderately serious problem), or 3 (severe problem). Total score from 0 to 48 with higher score indicating poorer health outcomes.

Total Score 43 items, each item scored on 4-point scale: 0-3, with total score from 0 (mild) to 129 (severe).

The subscales are stereotyped behaviors 6 items (subscale 0-18), self-injurious behaviors 8 items (subscale 0-24), Compulsive behaviors- 8 items (subscale 0-24), Ritualistic Behaviors 6 items (subscale from 0-18), Sameness 11 items (subscale 0-33), restricted behaviors 4 items (subscale 0-12). Total score is the sum of all items in the subscale with total score range from 0 to 129. Higher scores indicate greater symptom severity.

Standardized scores on the Adaptive behavior composite range from 20-160 with higher scores indicating better functioning.

16 items on ABC-SW subscale, Each item is scored as 0 (never a problem), 1 (slight problem), 2 (moderately serious problem), or 3 (severe problem). Total score from 0 to 48 with higher score indicating poorer health outcomes..

Repetitive Behavior Scale (RBS) - Total Score 43 items, each item scored on 4-point scale: 0-Behavior does not occur, 1-Behavior occurs and is a mild problem, 2-Behavior occurs and is a moderate problem, 3-Behavior occurs and is a severe problem. with total score from 0 (mild) to 129 (severe).

The subscales are stereotyped behaviors 6 items (subscale 0-18), self-injurious behaviors 8 items (subscale 0-24), Compulsive behaviors- 8 items (subscale 0-24), Ritualistic Behaviors 6 items (subscale from 0-18), Sameness 11 items (subscale 0-33), restricted behaviors 4 items (subscale 0-12). Total score is the sum of all items in the subscale with total score range from 0 to 129. Higher scores indicate greater symptom severity.

Participants in Study 2

The Clinical Global Impression - Severity scale (CGI-S) is a 7-point scale that requires the clinician to rate the severity of the patient's illness at the time of assessment, relative to the clinician's past experience with patients who have the same diagnosis. Considering total clinical experience, a patient is assessed on severity of mental illness at the time of rating 1, normal, not at all ill; 2, borderline mentally ill; 3, mildly ill; 4, moderately ill; 5, markedly ill; 6, severely ill; or 7, extremely ill.

The Clinical Global Impression - Improvement scale (CGI-I) is a 7 point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of the intervention. and rated as: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.

21 question tool, about caregiver strain, where each question uses a Likert scale where 1 is "Not at all" and 5 is "Very much." The full scale ranges from 21-105, where higher scores indicate more severe strain.

4 participants missing data from at least one data point

The SP is a standardized parent-completed questionnaire that assesses sensory processing and its impact on the functioning of children ages 3-10 yr. The 125 items represent behaviors that can be interpreted as responses to sensory experiences. The parent rates the observed frequency of these behaviors on a 5-point Likert scale (ranging from 1 always to 5 never). The tool consists of 14 sections, listed below, that refer to sensory processing, modulation, and behavioral and emotional responses. Subscale scores are listed below.

Each section's raw score is compared with a threshold value to determine a category of performance: typical performance, probable difference (1 standard deviation below the mean), and definite difference (2 standard deviations below the mean). A lower raw score means a greater difference.

The Short Sensory Profile is a caregiver report measure consisting of 38 items, each scored on a 1-point (always) to 5-point (never) Likert scale.

SSP Subscales Tactile Sensitivity (7 to 35) Taste/Smell Sensitivity (4 to 20), Movement Sensitivity (3 to 15), Under-Responsive/Seek Sensation (7 to 35) , Auditory Filtering (6 to 30), Low Energy/Weak (6 to 30), Visual/Auditory Sensitivity (5 to 25), with total scale from (38 to 190)

Lower scores indicate more sensory alterations.

Placebo