Overview
X-linked central congenital hypothyroidism with late-onset testicular enlargement is a very rare genetic condition that affects the thyroid gland and, later in life, the testes in males. The disease is caused by mutations in the IGSF1 gene located on the X chromosome. Because the thyroid gland does not receive proper signals from the pituitary gland in the brain, it does not produce enough thyroid hormone — a condition known as central hypothyroidism. Thyroid hormones are essential for normal growth, brain development, and metabolism, so low levels can lead to fatigue, weight gain, growth delays, and learning difficulties if not treated early. A distinctive feature of this condition is that affected males develop unusually large testes (macroorchidism) during or after puberty. This testicular enlargement is typically not painful but is an important clinical clue for diagnosis. Some individuals may also experience delayed puberty, low prolactin levels, and occasionally growth hormone deficiency. Because this is a form of central hypothyroidism, standard newborn screening programs — which typically measure TSH levels — may miss this condition, since TSH levels can appear normal even when thyroid hormone levels are low. Treatment involves lifelong thyroid hormone replacement therapy (levothyroxine), which can significantly improve symptoms and quality of life when started early. Regular monitoring by an endocrinologist is essential to adjust medication doses as the child grows. The condition is also sometimes referred to as IGSF1 deficiency syndrome.
Also known as:
Key symptoms:
Low thyroid hormone levels from birthFatigue and low energyWeight gain or difficulty losing weightDelayed growth or short statureEnlarged testes appearing during or after pubertyDelayed pubertyLearning difficulties or mild intellectual challengesConstipationDry skinSensitivity to coldLow prolactin levels in the bloodPossible growth hormone deficiencyDelayed bone maturation
X-linked recessive
Carried on the X chromosome; typically affects males more than females
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for X-linked central congenital hypothyroidism with late-onset testicular enlargement.
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Specialists
View all specialists →No specialists are currently listed for X-linked central congenital hypothyroidism with late-onset testicular enlargement.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to X-linked central congenital hypothyroidism with late-onset testicular enlargement.
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Caregiver Resources
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Family & Caregiver Grants
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Social Security Disability
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Questions for your doctor
Bring these to your next appointment
- Q1.Was my child's diagnosis delayed, and could this have affected their development?,How often should thyroid hormone levels be checked, and which blood tests are most important?,Should my child be tested for growth hormone deficiency or other pituitary hormone problems?,What should I expect regarding puberty and testicular enlargement?,Could this condition affect my child's fertility later in life?,Should female family members be tested to see if they are carriers?,Are there any clinical trials or new treatments being studied for this condition?
Common questions about X-linked central congenital hypothyroidism with late-onset testicular enlargement
What is X-linked central congenital hypothyroidism with late-onset testicular enlargement?
X-linked central congenital hypothyroidism with late-onset testicular enlargement is a very rare genetic condition that affects the thyroid gland and, later in life, the testes in males. The disease is caused by mutations in the IGSF1 gene located on the X chromosome. Because the thyroid gland does not receive proper signals from the pituitary gland in the brain, it does not produce enough thyroid hormone — a condition known as central hypothyroidism. Thyroid hormones are essential for normal growth, brain development, and metabolism, so low levels can lead to fatigue, weight gain, growth dela
How is X-linked central congenital hypothyroidism with late-onset testicular enlargement inherited?
X-linked central congenital hypothyroidism with late-onset testicular enlargement follows a x-linked recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does X-linked central congenital hypothyroidism with late-onset testicular enlargement typically begin?
Typical onset of X-linked central congenital hypothyroidism with late-onset testicular enlargement is neonatal. Age of onset can vary across affected individuals.