Evaluation of rat thyroid gland morphophysiological status after three months exposure to 50 Hz electromagnetic field.

Tissue & cell · 2003 · Harm · Low evidence

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HarmLow evidencePaper 5276

Study snapshot

PublicationTissue & cell · 2003

Study typeanimal

Reported directionHarm

Evidence ratingLow

Abstract

Objective of our study was to use morphophysiological criteria in order to determine the sensitivity of male rat thyroid gland to an extremely low frequency electromagnetic field (ELF-EMF) influence and the ability of the gland to repair after period of exposure. Animals were exposed to 50Hz, 50-500 microT ELF-EMF for 3 months when a part of them (group I) were sacrificed, while the rest of animals were subjected to recovery evaluation of the gland and sacrificed after 1 (group II), 2 (group III) and 3 (group IV) weeks. Histological and stereological analyses were performed on paraffin and semifine thyroid gland sections. Serum T3 and T4 were also determined. Histological and stereological analyses showed that the volume density of follicular epithelium and thyroid activation index decreased, while the volume density of colloid and capillary network increased in group I, II and III. The values of all these parameters in group IV were similar to corresponding controls. Serum T3 and T4 concentrations were significantly lower in all exposed animals, except in group I. Results of this study demonstrate that after significant morphophysiological changes caused by ELF-EMF exposure thyroid gland recovered morphologically, but not physiologically, during the investigated repair period.

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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

PopulationMale rats

Sample sizeNot supplied

ExposureELF · 0.05 MHz · 3 months exposure; recovery assessed at 1, 2, and 3 weeks post-exposure

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Rats exposed to 50 Hz (50–500 microT) ELF-EMF for 3 months showed decreased volume density of follicular epithelium and thyroid activation index and increased volume density of colloid and capillary network in groups assessed immediately and at 1–2 weeks post-exposure; by 3 weeks post-exposure these parameters were similar to controls. Serum T3 and T4 were significantly lower in all exposed groups except the group sacrificed immediately after exposure, suggesting morphological recovery but not physiological recovery over the repair period studied.

Outcomes measured

Thyroid histology (histological analysis)
Thyroid stereology (volume density of follicular epithelium, colloid, capillary network; thyroid activation index)
Serum T3 concentration
Serum T4 concentration
Morphological recovery after exposure

Limitations

Sample size not reported in abstract
Exposure source/setup details not described in abstract
Randomization/blinding not described in abstract
Only male rats studied; generalizability to other sexes/species not addressed
Recovery period limited to 3 weeks post-exposure

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "ELF",
    "source": null,
    "frequency_mhz": 0.05,
    "sar_wkg": null,
    "duration": "3 months exposure; recovery assessed at 1, 2, and 3 weeks post-exposure"
  },
  "population": "Male rats",
  "sample_size": null,
  "outcomes": [
    "Thyroid histology (histological analysis)",
    "Thyroid stereology (volume density of follicular epithelium, colloid, capillary network; thyroid activation index)",
    "Serum T3 concentration",
    "Serum T4 concentration",
    "Morphological recovery after exposure"
  ],
  "main_findings": "Rats exposed to 50 Hz (50–500 microT) ELF-EMF for 3 months showed decreased volume density of follicular epithelium and thyroid activation index and increased volume density of colloid and capillary network in groups assessed immediately and at 1–2 weeks post-exposure; by 3 weeks post-exposure these parameters were similar to controls. Serum T3 and T4 were significantly lower in all exposed groups except the group sacrificed immediately after exposure, suggesting morphological recovery but not physiological recovery over the repair period studied.",
  "effect_direction": "harm",
  "limitations": [
    "Sample size not reported in abstract",
    "Exposure source/setup details not described in abstract",
    "Randomization/blinding not described in abstract",
    "Only male rats studied; generalizability to other sexes/species not addressed",
    "Recovery period limited to 3 weeks post-exposure"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "extremely low frequency",
    "ELF-EMF",
    "50 Hz",
    "microtesla",
    "rat",
    "thyroid gland",
    "histology",
    "stereology",
    "T3",
    "T4",
    "recovery"
  ],
  "suggested_hubs": [
    {
      "slug": "occupational-exposure",
      "weight": 0.35,
      "reason": "Study involves ELF (50 Hz) magnetic field exposure at microtesla levels, relevant to occupational/environmental ELF exposure contexts."
    }
  ]
}

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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: 10.1016/s0040-8166(03)00029-6
PubMed: 12798131

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