Neurological consequences of adult-onset hypothyroidism.

Adult-onset hypothyroidism is associated with structural brain alterations, particularly in the hippocampus and prefrontal cortex.

• Recent studies have shown structural alterations beyond the previously recognized functional alterations.
• The hippocampus and prefrontal cortex are the primary regions affected by structural changes.
• These structural changes indicate that some neurological consequences of adult-onset hypothyroidism may be irreversible.

Hypothyroidism impairs synaptic plasticity, disrupts neurotransmitter signaling, and promotes neuroinflammation, leading to learning and memory impairments.

• These mechanisms were identified through neurophysiological and molecular studies.
• The disruption of multiple neural processes collectively contributes to cognitive dysfunction.
• Learning and memory impairments are downstream consequences of these molecular and physiological disruptions.

Adult-onset hypothyroidism affects adult neurogenesis, particularly in the hippocampal dentate gyrus.

• The hippocampal dentate gyrus is specifically identified as a region where neurogenesis is impacted.
• Adult neurogenesis is a process that continues throughout life and is disrupted by hypothyroid conditions.

Hypothyroidism has been linked to psychiatric disorders, including depression and anxiety, through its influence on the plasticity of the amygdala.

• The amygdala's plasticity is specifically identified as the neural substrate through which hypothyroidism influences psychiatric outcomes.
• Both depression and anxiety are identified as psychiatric consequences of adult-onset hypothyroidism.
• Amygdala plasticity changes represent a mechanism connecting thyroid hormone deficiency to mood disorders.

Adult-onset hypothyroidism contributes to cerebellar ataxia and peripheral neuropathy, impacting motor coordination and sensory processing.

• Both central (cerebellar) and peripheral nervous system components are affected by hypothyroidism.
• Cerebellar ataxia results in impaired motor coordination.
• Peripheral neuropathy affects sensory processing as a consequence of hypothyroidism.

Adult-onset hypothyroidism in part causes irreversible changes in brain structure, making prompt treatment crucial.

• The review distinguishes between reversible and irreversible neurological consequences of hypothyroidism.
• While adult-onset hypothyroidism has long been recognized as a reversible cause of cognitive impairment, some structural changes are now known to be irreversible.
• The irreversible nature of some changes underscores the clinical importance of early diagnosis and treatment.

Recent studies suggest a potential for thyroid hormone treatment beyond thyroid disorders, including in neurodegenerative and cognitive/psychiatric disorders.

• Thyroid hormone treatment is proposed as having therapeutic potential beyond its conventional use in thyroid field.
• Neurodegenerative disorders are among the conditions that may benefit from thyroid hormone treatment.
• Cognitive and psychiatric disorders are also identified as potential targets for thyroid hormone therapy.