Treatment Trial of Subclinical Hypothyroidism in Down Syndrome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Treatment Trial of Subclinical Hypothyroidism in Down Syndrome (NCT01832753), a randomized na study. The primary outcome is Change in Lipid Panel From Baseline at 6, 12 and 18 Months..

2. Clinical Question

The trial asks whether thyroid hormone replacement with levothyroxine changes cardiometabolic measures and quality of life in children and adolescents with Down syndrome who have persistent subclinical hypothyroidism. The primary endpoint is change in a lipid panel, measured from baseline through follow-up. The registry record describes a period of observation before randomization, so the treatment comparison concerns participants who proceeded to the randomized phase rather than everyone enrolled.

The stated hypothesis is that treatment could improve cardiometabolic health and quality of life. A hypothesis describes the question being tested, not a result. The registry record does not establish whether the observed trial data supported that hypothesis.

3. Trial Design

The study is titled “Treatment Trial of Subclinical Hypothyroidism in Down Syndrome,” with an official title focused on levothyroxine treatment and cardiometabolic outcomes in adolescents with Down syndrome. The sponsor is Children's Hospital of Philadelphia. The record lists the study as completed, with a start date of 2013-01 and primary completion on 2017-10-18. The listed enrollment is 12.

The design is randomized, double-blind, and parallel. The registry first describes an observation phase from months 0-6. Participants were observed to assess whether subclinical hypothyroidism persisted. Those who did not have the condition at the six-month visit did not proceed to treatment; the record also says participants with TSH >10 mIU/L during the observation phase were not considered for the next phase, although the accompanying description is truncated.

For the treatment phase, the record describes randomization to levothyroxine or placebo and a dose between 0.5 - 1 mcg/kg/day. It mentions treatment during months 6-12 and follow-up visits at month 7.5 and month 12. The phase heading refers to months 6-18, and the primary endpoint is assessed through month 18. The registry’s descriptions do not fully explain the treatment sequence across that full period. The primary-outcome population description refers to “Observation Only,” “Delayed Treatment,” and “Immediate Treatment” groups, but the available record does not fully specify their assignment and follow-up schedules.

Enrollment is not the same as the number contributing data to every follow-up assessment. The outcome description notes withdrawals before randomization and before or at the 12-month visit. Detailed participant flow and the number included in each endpoint analysis are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Observation Phase (Months 0-6)

Randomization Phase (Months 6-12)

Open Label Dose Phase (Months 12-18)

Analysis population for the primary outcome, as defined in the registry: 3 of the 12 participants ("Observation Only") were withdrawn prior to randomization due to normal TSH. 1 of the 4 Delayed Treatment group participants self-withdrew before their 12 month visit. 1 of the 5 Immediate Treatment participants withdrew due to elevated TSH at their 12 month visit, 1 and self-withdrew before their 12 month visit.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Lipid Panel From Baseline at 6, 12 and 18 Months., measured over baseline, 6 months, 12 months & 18 months.

The primary endpoint is change in lipid panel from baseline at 6, 12 and 18 months. The record specifies that the lipid panel is measured using a fasting blood draw and reports the outcome scale as mg/dL. It describes the summary measure as the median and the measure of spread as the inter-quartile range.

A lipid panel collects measures of blood lipids. In general, lipid measurements are used to characterize aspects of cardiometabolic health; tracking change over time can describe how those measures vary during follow-up. The trial’s stated interest in cardiometabolic outcomes explains why the lipid panel was selected as its primary endpoint. The record does not identify the individual lipid components, their separate analysis methods, or a single prespecified summary contrast between treatment groups.

Change from baseline compares a follow-up measurement with the starting measurement for the outcome. To interpret such change as a treatment effect, readers need to know how the groups were compared, how repeated measurements were handled, and how missing follow-up values were treated. Those analytical details are not reported in the registry record.

The record does not include lipid-panel values at baseline or follow-up, changes in the groups, a between-group estimate, or a confidence interval. It therefore documents what was intended to be measured, but does not allow the magnitude or precision of a treatment-related difference to be assessed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Statistical methods determine how measurements are converted into estimates and how uncertainty is described. The registry record names the primary measure and the summary format, but does not report the analysis used to compare treatment groups. The explanations below are general statistical context, not a description of unreported trial procedures.

What does the median describe?

The median is the middle value when observations are ordered. It is a way to describe the center of a distribution and is less sensitive to extreme values than the mean. The inter-quartile range describes the spread of the middle portion of the observations. Reporting a median and inter-quartile range can be useful when measurements are skewed or when unusually high or low values would make a mean and standard deviation less representative.

These summaries describe a group’s measurements; by themselves, they do not estimate a randomized treatment effect. To assess a treatment contrast, an analysis must define how the groups are compared, whether the comparison concerns follow-up values or change from baseline, and how values measured at multiple follow-up times are handled. The registry record does not report those choices or the resulting estimates.

Why does randomization matter?

In general, random assignment aims to make treatment groups comparable at the start of a trial, including with respect to factors that are measured and factors that are not measured. A comparison based on randomized assignment can therefore help estimate the effect of assignment to treatment under the assumptions of the analysis. Randomization does not guarantee that groups will be identical, particularly in a small trial, and it does not remove the need to account for missing data or deviations from the planned treatment.

The record labels the study randomized, double-blind, and parallel, and lists placebo and treatment groups. It does not report the randomization sequence method, allocation concealment procedures, or details of how blinding was maintained. Those items are not reported in the registry record.

How should repeated measurements be understood?

The primary outcome is measured at baseline and at several follow-up visits. Repeated measurements from the same participant are related, rather than independent observations. In general, an analysis of repeated measurements needs to account for that within-participant relationship. An analysis may estimate changes separately at each visit or use a model to describe the pattern over time, but the registry record does not identify which approach was used.

It is also important to distinguish change within each group from a difference in change between groups. A group’s median may move over time without establishing that its change differs from the comparator’s change. A direct contrast between randomized groups, with an uncertainty estimate, is needed to quantify the treatment comparison. No such contrast is posted for the lipid endpoint.

What do confidence intervals and p-values contribute?

In general, a confidence interval expresses uncertainty around an estimated contrast. A narrow interval indicates greater precision under the statistical model, whereas a wide interval indicates that a range of effects remains compatible with the observed data and method. The interval should be interpreted together with the estimate and the clinical question, not as a stand-alone verdict.

A p-value describes how unusual data at least as discrepant as those observed would be under a specified null hypothesis and statistical model. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The registry record reports no p-value or confidence interval for the primary endpoint. It also does not report a statistical analysis plan or specify a primary treatment contrast.

What does over-dispersion mean in general?

Over-dispersion occurs when observed variability is greater than a statistical model assumes. If a model understates variability, standard errors can be too small and uncertainty intervals can be too narrow. Methods that account for over-dispersion can improve uncertainty estimates when the data and model warrant them. This is general context only: the registry record does not report a count model, an over-dispersion assessment, or a method used to address it. The primary lipid outcome is described using medians and inter-quartile ranges, and no fitted model is specified.

What can planning calculations tell readers?

In general, a sample-size calculation uses design assumptions to estimate how many participants would be needed to detect a specified effect with a chosen significance level and power. A planning illustration based on an observed effect is a hypothetical calculation, not an additional result from the trial and not observed power. The registry lists assumptions of a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects expressed as fractions of the observed effect. Numerical planning illustrations are not reported in the registry record. The record also does not report its original sample-size justification or the assumptions used when planning the trial.

10. Multiplicity, Missing Data and Analysis Populations

The primary lipid outcome is described at baseline and at 6, 12 and 18 months, and the registry lists a secondary quality-of-life outcome at the same follow-up times. Testing multiple outcomes or time points can raise the issue of multiplicity: when several statistical comparisons are made, the chance of at least one apparently unusual result can increase. In general, a statistical plan may identify a primary contrast or use an adjustment approach to address multiple testing. The registry record does not report whether multiplicity was addressed, which comparisons were considered primary, or how any adjustment was made.

The record does not report an analysis plan, a missing-data method, or whether analyses were based on all randomized participants, participants who completed follow-up, or another analysis population. These details matter because a complete-case analysis can differ from an analysis that uses all available observations or makes model-based assumptions about missing values. No missing-data assumptions or sensitivity analyses are reported in the registry record.

The primary-outcome description notes withdrawals: 3 of the 12 participants were withdrawn before randomization because TSH was normal; 1 of the 4 Delayed Treatment group participants self-withdrew before the 12-month visit; and 1 of the 5 Immediate Treatment participants withdrew due to elevated TSH at the 12-month visit. The record does not give a complete account of missing lipid measurements at each visit or explain how these withdrawals affected the endpoint analysis.

Because the endpoint values and analysis are not posted, the impact of missing observations and multiple follow-up comparisons cannot be evaluated. Those details are not reported in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events and other adverse events by study phase or group. In the Observation Phase, 0 serious adverse events were reported among 12 at risk, and 1 other adverse event was reported among 12 at risk. In the Randomization Phase - Placebo group, 0 serious adverse events were reported among 4 at risk, and 4 other adverse events were reported among 4 at risk. In the Randomization Phase - Treatment group, 0 serious adverse events were reported among 5 at risk, and 4 other adverse events were reported among 5 at risk. In the Open Label Treatment Phase, 0 serious adverse events were reported among 6 at risk, and 1 other adverse event was reported among 6 at risk.

Deaths are listed as 0 in each reported group. The record lists no top serious adverse-event terms. These figures are registry counts, not estimates of a treatment effect. The observation and open-label phases are distinct from the randomized placebo comparison, so their counts should not be read as randomized between-group contrasts. Phase counts may also refer to different periods of participation; they should not be added to create a participant total.

The registry record does not provide event descriptions for the other adverse events, severity detail beyond the serious-event classification, or an assessment of whether events were caused by treatment. The counts therefore describe what was reported in the safety fields, but do not establish comparative risk or causation.

12. What the Result Does, and Does Not, Mean

The record documents a clinical question, a randomized and double-blind design, an intended primary endpoint, and safety counts. It does not report the primary lipid measurements or a statistical comparison. As a result, it does not show the direction or size of any treatment-group difference in lipid-panel change, nor how precisely such a difference was estimated.

This distinction is important: a trial’s hypothesis and design explain what investigators intended to test, whereas results require observed measurements and an analysis. The hypothesis that levothyroxine could improve cardiometabolic health and quality of life is stated in the trial summary. It should not be read as evidence that either outcome improved. The quality-of-life outcome is listed as secondary, but its numerical results are not reported in the registry record either.

The safety fields report no serious adverse events in the listed groups and report other adverse events. Those entries do not determine whether a treatment caused or prevented an event, and they do not answer the primary lipid question. The absence of a posted primary analysis also means that the safety counts cannot be paired with an estimate of benefit to characterize an overall benefit-risk balance.

The record’s enrollment and withdrawal information further limits interpretation of follow-up. Some participants did not proceed to randomization, and the outcome description notes withdrawals during later follow-up. Without a complete participant flow, endpoint-specific counts, and missing-data methods, the amount and handling of unavailable outcome data cannot be assessed.

Accordingly, the registry supports statements about the study’s design and the outcomes it set out to assess. It does not support a claim about whether levothyroxine did or did not change lipid measures, quality of life, or cardiometabolic health in the study population. Such a conclusion would require outcome results and a transparent analysis that are not reported in the registry record.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between a registered study design and an interpretable outcome analysis. The registry gives the core framework—a randomized, double-blind, parallel comparison—and identifies a primary endpoint measured over follow-up. Those features define the intended question, but do not by themselves reveal what the data showed.

The observation phase is also relevant to the population being compared. Participants were assessed for persistent subclinical hypothyroidism before entering treatment randomization, and the record says participants with normal TSH at the six-month visit did not proceed. Thus, the randomized treatment question is narrower than a question about all enrolled children and adolescents with Down syndrome. Clear reporting of screening, eligibility, randomization, and follow-up helps readers understand the population to which an estimate would apply.

The primary endpoint includes repeated measurements, while the record reports median and inter-quartile range as summary statistics. Readers need an explicit between-group analysis and uncertainty estimate to distinguish descriptive changes from treatment contrasts. The registry does not report that analysis. It also does not report multiplicity procedures or missing-data methods, which are important for interpreting results across several follow-up times and outcomes.

Finally, the safety fields show why counts need context. Counts are reported separately across observation, randomized, and open-label phases, and those phases do not all represent the same kind of comparison. Keeping phase-specific denominators and study pathways visible avoids treating the entries as a single randomized contrast.

The statistical significance of this record lies in the questions it highlights: whether outcome reporting is complete, whether analyses match the design, and whether estimates are presented with their uncertainty. Without the posted endpoint analysis, those questions remain unanswered for this trial.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

A central limitation of the registry record is the absence of numerical primary-outcome results. Although it specifies lipid-panel change and the planned measurement times, it provides no group-specific measurements, change estimates, or treatment contrast. The record lists 0 analyses. Without an estimate and its uncertainty, neither magnitude nor precision can be evaluated.

The outcome description is incomplete. It identifies a median and inter-quartile range but does not name the individual lipid components or specify the comparison used to assess change. The record refers to observation-only, delayed-treatment, and immediate-treatment groups, while the treatment-phase description does not fully explain the schedule through month 18. The available descriptions therefore do not give a complete account of the analysis pathways.

The enrollment was 12, and the endpoint description notes exclusions from randomization and withdrawals during follow-up. The registry does not report participant flow at every assessment, the number contributing measurements to each endpoint analysis, or the method used to handle missing outcomes. This prevents assessment of how complete follow-up was and whether the analytic population differed from the randomized population.

The record does not report the statistical analysis plan, the primary contrast, multiplicity handling, or the original sample-size justification. Numerical results for the listed secondary quality-of-life outcome are also not reported in the registry record. Safety reporting is limited to phase-specific counts, without event descriptions for other adverse events or causal assessments. These reporting gaps limit interpretation; they do not establish that analyses or results were absent outside the registry.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Treatment Trial of Subclinical Hypothyroidism in Down Syndrome — NCT01832753.
• Registry record last updated 2019-09-06; status last verified 2019-09.
• Results first posted 2019-06-13.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

NCT01832753 is a completed randomized, double-blind, parallel trial sponsored by Children's Hospital of Philadelphia. It enrolled 12 participants and examined levothyroxine treatment for subclinical hypothyroidism in children and adolescents with Down syndrome. The design included an observation phase before treatment randomization to assess persistence of the thyroid condition, followed by placebo or levothyroxine in the randomized phase.

The primary outcome was change in lipid panel from baseline at 6, 12 and 18 months, measured by fasting blood draw and summarized as median with inter-quartile range in mg/dL. Quality-of-life change was listed as a secondary outcome. The registry reports safety counts by study phase, but does not report numerical primary or secondary outcome results, a treatment-effect estimate, or an analysis of the primary endpoint. Its listed analysis count is 0. Thus, the record describes the study question and design but does not permit interpretation of the lipid-panel treatment contrast.