Introduction
The pineal gland is a photo-neuro-endocrine organ situated inside the brain, that secretes serotonin, melatonin and N,N-dymethyltriptamine. This narrative review will address the latest information gathered on this function of the gland as well as the unknown roles it may have. The different histological and pathological findings of the pineal gland have demonstrated a role in clinical manifestations of numerous endocrine, neurological and psychiatric pathologies.

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The morphological and functional characteristics of the pineal gland.

Background: The most common disorders of the thyroid gland are hyperthyroidism and hypothyroidism. Both have been linked to cell damage.Aim of Work: This study was designed to evaluate the effect of melatonin administration on the testis of both hyperthyroidic and hypothyroidic adult male albino rats models.Materials and Methods: Fifty adult male albino rats were used in this study and divided into five groups; ten rats each. Control group (G1) was given distilled water. Hyperthyroidic group (G2) was given thyroxin (0.2 mg/kg b.w). Hyperthyroidic+melatonin group (G3) was given thyroxin (0.2 mg/kg b.w) and melatonin (2.5 mg / kg b.w). Hypothyroidic group (G4) was given carbimazole (1.35 mg/kg b.w). Hypothyroidic+melatonin group (G5) was given carbimazole (1.35 mg/kg b.w) and melatonin (2.5 mg / kg b.w). All the treatments were given orally for 15 days. At the end of the study, the animals of all groups were sacrificed and their testes were rapidly dissected out. The testicular mass was calculated. Testicular specimens of each group were processed for light and electron microscopic studies.Results: The testicular mass was significantly decreased in both hyperthyroidic group (G2) and hypothyroidic group (G4) when compared with the control. Light and electron microscopy of the hyperthyroidic group (G2) and hypothyroidic group (G4) showed seminiferous tubular germ cells disorganization with increased intercellular spaces, necrosis and cellular damage. Melatonin supplementation to rats given Thyroxin (G3) improved the testicular mass and the cell damage. On the contrary, melatonin supplementation to rats given carbimazole (G5) did not show any improvement on both morphometrical and histological levels.Conclusion: It was concluded that simultaneous melatonin administration effectively depresses the negative effects of hyperthyroidism but not hypothyroidism on the adult male rat testis.

https://ejh.journals.ekb.eg/article_3852_5348a3257041ae25421c1757aae202a7.pdf

Effects of Simultaneous Melatonin Administration on the Testis of the Experimentally Induced Hyper- and Hypothyroidism in the Adult Male Albino Rat

pineal-thyroid karyomarphology and function in resonse to diversely altered serum T4 levels in rat (rattus rattus)

In the present investigation, influence of experimentally induced hypothyroidism on pineal karyomorphology was studied in three different species of animals – post pubertal male mice (Mus musculus), adult male rats (Rattus rattus) and neonatal male chicks (Gallus domesticus). Twenty-two animals of each species group were used, divided into two sets of experimental groups, Group A the control group and the other Group B the treated group. In Group A, eleven control animals of each species were given normal pelleted feed and normal drinking water ad libitum. In GroupB, the adult male mice (N=11), rats (N=11) and chicks (N=11) were supplied with normal pelleted feed and methimazole dissolved in drinking water (at a dose of 1 gm/l). After expiry of the experimental period of fifteen consecutive days each set of control and treated animals were divided into two groups and killed by etherisation. In the first set of control (N=6) and treated (N=6) experiments, animals were considered for histological studies. The second set of control (N=5) and treated (N=5) experiments, animals were considered for T4 assay. Present data reveal that methimazole caused a significant reduction reaching about detection value of serum T4 (μg/dl) levels in all the three species of animals. Such hypothyroid animals showed inhibition of the pineal gland activity as seen from significantly decreased pinealocyte nuclear diameter (μm) in all three species of animals, along with an increased pinealocyte nuclear density per microscopic field in mice and rats. Our study indicates that methimazole induced chemical hypothyroidism inhibits pineal gland activity in both mammals and birds.

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A Comparative Study Indicates Methimazole Induced Chemical Hypothyroidism Causes Inhibition of Pineal Gland Karyomorphology in Three Different Species of Animals

B.R. Sinha

Papers

A Comparative Study Indicates Methimazole Induced Chemical Hypothyroidism Causes Inhibition of Pineal Gland Karyomorphology in Three Different Species of Animals