Human growth hormone is important in many aspects of growth and development. For children living with growth hormone deficiency, it can involve more than just physical growth differences. Cognitive functions related to learning can also be affected.

Growth hormone deficiency (GHD) occurs when the pituitary gland does not produce enough human growth hormone (HGH). Also referred to as just “growth hormone,” HGH promotes developmental growth in nearly every organ and tissue in the body. It is most influential during childhood and adolescence, as it plays an active part in the linear growth of bone and soft tissue.

Due to the important role HGH plays in age-related growth, an insufficient production of HGH can affect a child’s overall development. Common characteristics seen in children with GHD include:

  • shorter stature
  • delayed growth milestones — e.g., late tooth eruption or puberty
  • atypical distribution of fat around the face and midsection

GHD is both a condition itself and a feature of other disorders, such as Turner syndrome and Prader-Willi syndrome. Depending on its cause, it may occur during childhood or adulthood.

Childhood-onset GHD, known as congenital GHD, affects more than physical development. It can affect various processes in the body, including those related to cognitive functions such as memory and learning.

GHD may affect how the brain develops in childhood. A cross-sectional 2023 imaging study found that children living with GHD showed certain changes in brain structure — including variations in thickness and tissue integrity — compared with children without GHD.

The researchers attributed this association to the interaction between HGH and insulin-like growth factor 1 (IGF-1), a hormone stimulated by HGH that also promotes cellular growth and differentiation during development.

In GHD, not enough HGH leads to reduced levels of circulating IGF-1. This deficiency in IGF-1 can impair the growth of bones and soft tissues and may reduce the effectiveness of any available HGH.

Not only can GHD affect the brain’s structure, it can affect its function. The same HGH/IGF-1 pathway that influences thickness and volume in parts of the brain also affects hormone-related brain functions essential to cognition.

Both HGH and IGF-1 can cross the blood-brain barrier, influencing hormones in parts of the brain, such as the hippocampus. The hippocampus, a small structure within the medial temporal lobe, facilitates memory formation, learning, emotional regulation, and spatial navigation (the ability to navigate through an environment).

When a person is HGH deficient, it can affect brain hormones that serve as important neurotransmitters, altering how effectively parts of the brain communicate. Not enough HGH can also impair the formation and plasticity (adaptability) of neurons, which is important for memory consolidation and learning.

If a child receives a GHD diagnosis, caregivers may notice cognitive challenges that present in the following ways:

  • difficulty remembering recent events or information learned
  • taking longer to solve problems
  • finding it difficult to stay on task or concentrate
  • not being able to follow complex instructions
  • emotional reactivity
  • mood swings
  • becoming easily frustrated

The structural and functional changes in the brain in GHD may affect intelligence for some, but not all, children.

Cognitive impairment in GHD does not automatically represent below-average intelligence. Intelligence is measured by assessing certain cognitive functions, such as memory, processing speed, reasoning, and verbal comprehension.

While GHD may pose certain learning or memory challenges, intelligence is multifaceted and may not be significantly affected by one or two impaired cognitive skills.

In other words, just because GHD can make learning more challenging does not always mean it negatively affects a child’s capacity for learning.

If left untreated, the physical and mental challenges in childhood-onset GHD can persist into adulthood. Short stature can become permanent, and some children may never reach their full growth potential, even with treatment.

While it is true the body requires less HGH in adulthood, being deficient throughout life can still cause long-term complications, such as:

  • reduced bone mineral density
  • increased risk for osteoporosis and fractures
  • decreased muscle strength and exercise capacity
  • reduced insulin sensitivity and glucose tolerance
  • increased risk for type 2 diabetes
  • elevated low-density lipoprotein (LDL) cholesterol
  • increased risk for cardiovascular disease
  • abdominal obesity
  • cognitive impairment
  • reduced overall quality of life

Some 2023 research suggests GHD may increase mortality rates in certain conditions, such as hypopituitarism, a disorder in which the pituitary gland does not secrete enough hormones in general. The pituitary gland is responsible for producing nine different hormones, including HGH.

Treating GHD can improve physical health, cognitive function, and overall intellectual performance. Doctors can successfully treat GHD by supplementing the body with recombinant HGH, a manufactured form of HGH created using DNA-combining technology.

HGH therapy starts as soon as a person receives a diagnosis of GHD, and gradually increases to its highest dose during puberty. Once a person reaches physical maturity, HGH therapy usually stops, though some people may need to continue supplementation throughout adulthood.

A small 2015 study found treating GHD with HGH therapy improved children’s overall intelligence quotient (IQ), with the most notable improvements in fluid intelligence — a person’s logical reasoning, mental adaptability, and problem-solving ability in unique situations.

Research from 2020 notes that HGH replacement therapy for GHD can significantly improve memory, learning, mental alertness, motor skills, and motivation. It can support brain development and proper function, promoting the development of neural networks during childhood as well as the restoration of neural plasticity in adulthood.

Treating GHD as soon as possible may also improve health outcomes. A 2023 review notes early treatment can result in significant catch-up growth and, if started within the first few years of life, may help prevent structural damage to the brain and preserve neurological development.

Growth hormone deficiency, or GHD, is known for certain physical traits such as short stature, but it can also affect cognitive functions involved with learning. Changes in the brain’s structure and function from GHD can create challenges related to memory, problem-solving, and concentration, among many others.

However, cognitive deficits do not always represent lower intelligence in children with GHD. Intelligence is a complex concept involving multiple aspects of cognition, so it is possible to experience cognitive deficits in one or two areas without it affecting overall intelligence.

Learning challenges associated with GHD may be prevented or improved through timely treatment with HGH therapy.