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

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.

AI evidence extraction

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

Suggested hubs

• occupational-exposure (0.35)
  Study involves ELF (50 Hz) magnetic field exposure at microtesla levels, relevant to occupational/environmental ELF exposure contexts.

{
    "study_type": "animal",
    "exposure": {
        "band": "ELF",
        "source": null,
        "frequency_mhz": 0.05000000000000000277555756156289135105907917022705078125,
        "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": 0.7800000000000000266453525910037569701671600341796875,
    "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": 0.34999999999999997779553950749686919152736663818359375,
            "reason": "Study involves ELF (50 Hz) magnetic field exposure at microtesla levels, relevant to occupational/environmental ELF exposure contexts."
        }
    ]
}

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