Researchers in India measured how boys’ bodies develop from ages 5 to 20, focusing on two key changes during puberty: testicular size and a hormone called testosterone. They studied over 1,000 healthy boys and created detailed growth charts showing what’s normal at each age. The study found that the biggest changes happen between ages 11 and 15, and that boys with higher muscle mass and bone density tend to have larger testicles. These new charts help doctors know what’s healthy and normal for Indian boys, which is important because growth patterns can differ between populations.

The Quick Take

  • What they studied: How testicular size and testosterone hormone levels change as boys grow from age 5 to 20, and what factors influence these changes
  • Who participated: 1,022 healthy boys aged 5-20 years from schools and community centers in northern India, studied between 2019 and 2023
  • Key finding: Both testicular size and testosterone levels increase significantly with age, with the most dramatic changes happening between ages 11-15. Boys with more muscle and bone mass tended to have larger testicles
  • What it means for you: Doctors now have reliable growth charts to determine if a boy’s development is on track. If you’re a parent or young person concerned about development, these charts help doctors give accurate answers about what’s normal

The Research Details

This was an observational study where researchers measured boys at one point in time rather than following them over years. They recruited 1,022 healthy boys from schools and community centers across northern India between 2019 and 2023. For each boy, they measured testicular volume using a special tool called Prader’s orchidometer (a set of beads of different sizes used for comparison) and measured testosterone levels through a blood test. They also collected other measurements including height, weight, muscle mass, bone mass, and several hormone levels to understand what factors might influence testicular development.

Creating these growth charts is important because normal development varies between different populations and regions. Previous reference values came from other countries, which may not accurately represent Indian boys. Having local, population-specific charts helps doctors distinguish between normal variation and actual medical problems that need treatment.

This study has several strengths: it’s a large sample size (over 1,000 boys), it’s recent data (2019-2023), and it includes detailed measurements beyond just the main variables. However, it only includes boys from one region of India, so results may not apply equally to all Indian populations. The study was observational rather than experimental, meaning it shows associations but can’t prove cause-and-effect relationships.

What the Results Show

The study clearly showed that both testicular volume and testosterone levels increase steadily with age, with the most noticeable changes occurring between ages 11 and 15 years—the typical puberty window for boys. Before age 11, changes were gradual, and after age 15, the rate of increase slowed down. The researchers created detailed growth charts (called centile curves) showing the normal range at each age, similar to height and weight charts used by pediatricians. These charts show what’s typical for the 10th, 25th, 50th, 75th, and 90th percentiles, helping doctors identify whether a boy’s development is ahead, on track, or behind for his age.

When researchers looked at other factors, they found that boys with higher body mass index (BMI), more muscle mass, and greater bone mass tended to have larger testicles. Interestingly, vitamin D levels and albumin (a blood protein) showed no significant relationship with testicular development. The study also confirmed that two hormones—luteinizing hormone (LH) and follicle-stimulating hormone (FSH)—which control puberty, were strongly associated with testicular size, which makes biological sense since these hormones trigger puberty.

Previous growth charts for testicular development and testosterone came primarily from European and American populations. This study provides the first large-scale, population-specific data for Indian boys, which is important because growth patterns and timing of puberty can vary between ethnic groups and geographic regions. These new Indian reference values fill an important gap in medical literature and provide more accurate benchmarks for Indian pediatricians.

The study only included boys from one center in northern India, so results may not represent all Indian populations equally, especially those from southern or eastern India. Because it was a one-time measurement study rather than following boys over time, researchers couldn’t track individual development patterns. The study also only included ‘apparently healthy’ boys, so results may not apply to boys with medical conditions or nutritional deficiencies.

The Bottom Line

These growth charts should be used by pediatricians and endocrinologists to assess whether a boy’s pubertal development is progressing normally (moderate to high confidence). If a boy’s development appears significantly ahead or behind the normal range for his age, further evaluation by a doctor is warranted. Parents and young people should not self-diagnose based on these charts but should discuss any concerns about development with a healthcare provider (high confidence).

Pediatricians and endocrinologists in India should use these charts for clinical assessment. Parents of boys aged 5-20 in India may find this helpful for understanding normal development. Boys themselves may be reassured knowing what’s typical for their age. This is less relevant for populations outside of India unless they have similar ethnic backgrounds. Anyone with specific concerns about development should consult their doctor rather than relying on charts alone.

Changes in testicular volume and testosterone happen gradually over several years. The most noticeable changes occur between ages 11-15, but the entire process from age 5 to 20 is gradual. If a boy seems significantly behind or ahead of the normal range, evaluation should happen relatively soon, but development doesn’t need to match the exact average—there’s a wide normal range.

Want to Apply This Research?

  • Track annual measurements of height, weight, and BMI alongside doctor visits. Note the age when puberty signs first appear (like body hair growth or voice changes) to compare against typical timelines
  • Use the app to set reminders for annual check-ups with a pediatrician, especially during ages 10-16 when puberty occurs. Record any concerns about development to discuss with healthcare providers
  • Create a growth timeline in the app showing height and weight measurements over years, with visual comparison to normal growth curves. This helps identify whether development is tracking normally without obsessive monitoring

This research provides reference values for assessing normal development in Indian boys but should not be used for self-diagnosis. Individual development varies widely and is influenced by genetics, nutrition, and health status. If you have concerns about a boy’s growth or pubertal development, consult with a qualified pediatrician or endocrinologist who can perform proper clinical evaluation. These charts are tools for healthcare providers, not substitutes for professional medical advice.