Light and electron microscopic study of the thyroid gland in rats exposed to power-frequency electromagnetic fields.

The Journal of experimental biology · 2006 · Harm · Low evidence

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HarmLow evidencePaper 5108

Study snapshot

PublicationThe Journal of experimental biology · 2006

Study typeanimal

Reported directionHarm

Evidence ratingLow

Abstract

The effect of 50 Hz electromagnetic field (EMF) on thyroid gland was studied using light and transmission electron microscopes. Two-month-old male rats were exposed to an EMF (100-300 microT, 54-160 V m(-1)) for 4 h a day, 5 days a week for 1 month. A predominance of microfollicles with less colloid content and dilated blood capillaries was found in the EMF group. Stereological counting showed a statistically significant increase of the volume density of follicular epithelium, interfollicular tissue and blood capillaries as well as the thyroid activation index, as compared to the controls. The volume density of colloid significantly decreased. Ultrastructural analysis of thyroid follicular cells in the EMF group revealed the frequent finding of several colloid droplets within the same thyrocyte with the occasional presence of large-diameter droplets. Alterations in lysosomes, granular endoplasmic reticulum and cell nuclei compared to the control group were also observed. Taken together, the results of this study show the stimulative effect of power-frequency EMF on thyroid gland at both the light microscope and the ultrastructural level.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeanimal

Effect directionharm

PopulationTwo-month-old male rats

Sample sizeNot supplied

ExposureELF · 4 h/day, 5 days/week for 1 month

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Rats exposed to a 50 Hz EMF (100–300 microT, 54–160 V/m) showed predominance of microfollicles with less colloid and dilated blood capillaries versus controls. Stereological counting found significant increases in volume density of follicular epithelium, interfollicular tissue, and blood capillaries and in thyroid activation index, with a significant decrease in colloid volume density. Ultrastructural changes in follicular cells (e.g., multiple colloid droplets, alterations in lysosomes, granular endoplasmic reticulum, and nuclei) were observed; authors interpret findings as a stimulative effect on the thyroid gland.

Outcomes measured

Thyroid gland histology (light microscopy)
Thyroid gland ultrastructure (transmission electron microscopy)
Stereological measures: volume density of follicular epithelium, interfollicular tissue, blood capillaries, colloid
Thyroid activation index

Limitations

Sample size not reported in abstract
Animal study; generalizability to humans is uncertain
Exposure source/context not specified beyond field parameters

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "ELF",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "4 h/day, 5 days/week for 1 month"
  },
  "population": "Two-month-old male rats",
  "sample_size": null,
  "outcomes": [
    "Thyroid gland histology (light microscopy)",
    "Thyroid gland ultrastructure (transmission electron microscopy)",
    "Stereological measures: volume density of follicular epithelium, interfollicular tissue, blood capillaries, colloid",
    "Thyroid activation index"
  ],
  "main_findings": "Rats exposed to a 50 Hz EMF (100–300 microT, 54–160 V/m) showed predominance of microfollicles with less colloid and dilated blood capillaries versus controls. Stereological counting found significant increases in volume density of follicular epithelium, interfollicular tissue, and blood capillaries and in thyroid activation index, with a significant decrease in colloid volume density. Ultrastructural changes in follicular cells (e.g., multiple colloid droplets, alterations in lysosomes, granular endoplasmic reticulum, and nuclei) were observed; authors interpret findings as a stimulative effect on the thyroid gland.",
  "effect_direction": "harm",
  "limitations": [
    "Sample size not reported in abstract",
    "Animal study; generalizability to humans is uncertain",
    "Exposure source/context not specified beyond field parameters"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "50 Hz",
    "power-frequency",
    "ELF-EMF",
    "thyroid gland",
    "rat",
    "microT",
    "V/m",
    "light microscopy",
    "transmission electron microscopy",
    "stereology",
    "thyroid activation index"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.35,
      "reason": "Power-frequency (50 Hz) ELF exposure may relate to occupational-type EMF contexts, though the specific source is not stated."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1242/jeb.02375
PubMed: 16916968

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