Developmental thyroid hormone insufficiency and brain development: a role for brain-derived neurotrophic factor...

Area of Science:

• Neuroendocrinology
• Developmental Neuroscience
• Environmental Health

Background:

• Thyroid hormones (TH) are vital for normal brain development.
• Prenatal TH disruption, even mild, can lead to neuropsychological deficits.
• Neurotrophins, particularly brain-derived neurotrophic factor (BDNF), are implicated in nervous system development and function.

Purpose of the Study:

• To review recent developments in thyroid hormone's effects on the nervous system.
• To describe an animal model for studying low-level TH insufficiency.
• To examine the in vivo literature on TH-mediated alterations in neurotrophins, especially BDNF, and their contribution to brain impairments.

Main Methods:

• Literature review of thyroid hormones and neurotrophins.
• Description of a novel animal model for subclinical hypothyroidism.
• Analysis of in vivo studies on BDNF and TH interactions.

Main Results:

• Observed alterations in BDNF protein and gene expression vary significantly with model, age, and brain region.
• Limited research exists on non-severe TH deprivation models, with sparse dose-response data.
• Reaching a consensus on BDNF's role is challenging due to methodological differences across studies.

Conclusions:

• The direct role of BDNF in thyroid-mediated brain effects is not yet compelling.
• Further research should explore other neurotrophins, moderate TH insufficiency, and younger ages.
• Investigating BDNF in response to synaptic activity may clarify thyroid hormone's role in synaptic function.