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How Thyroid Hormones Influence Metabolism, Mood, and the Brain

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Thyroid hormones are chemical messengers produced by the thyroid gland that circulate through the bloodstream and influence cells throughout the body. Their primary role is the regulation of metabolism, but thyroid hormones also affect brain function, mood, cognition, and behavior. The Brain–Pituitary–Thyroid Axis Thyroid function is regulated through a three-step hormonal system known as the hypothalamic-pituitary-thyroid (HPT) axis. The hypothalamus, located in the brain, releases thyrotropin-releasing hormone (TRH). TRH stimulates the pituitary gland to release thyroid-stimulating hormone (TSH). TSH then stimulates the thyroid gland in the neck to produce thyroid hormones, primarily T4 (thyroxine). T4 is subsequently converted into the more biologically active hormone T3 (triiodothyronine). This regulatory system allows the brain to influence how much thyroid hormone circulates throughout the body. Thyroid Hormones and Metabolism One of the major functions of thyroid hormones is to ...
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Thin, Fragile Skin, Bruising and Slow Healing: Hydrocortisone/Glucocorticoid Effects and the Possible Relevance of sPRP and BPCP

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Focused summary. The combination of thin or fragile skin, easy bruising and slow wound healing is compatible with chronic glucocorticoid effects on skin. Dryness, wrinkles and sagging can occur in the same clinical picture, but they are less specific because aging, sun exposure, psoriasis and impaired skin-barrier function can produce similar changes. The key question is therefore not whether every symptom is caused by hydrocortisone, but whether cumulative glucocorticoid exposure is contributing to dermal atrophy and poor repair. 1. Why glucocorticoids can produce this skin pattern Glucocorticoids can suppress fibroblast activity and collagen synthesis. With less dermal collagen and structural support, skin may become thinner, more translucent and easier to tear. Reduced dermal support makes small blood vessels less protected, which can contribute to easy bruising or purpura. Glucocorticoid exposure can impair normal tissue-repair processes, making wounds or skin tears heal more slowl...
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Phototoxic Dermatitis Induced by Doxycycline and Plant-Derived Furocoumarins: Different Mechanisms, Shared Clinical Consequences

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Abstract Phototoxic dermatitis is a non-immunologic inflammatory reaction that occurs when photosensitizing substances interact with ultraviolet A (UV-A) radiation. It differs fundamentally from an allergic drug reaction, which is immune-mediated and may present with life-threatening symptoms such as airway swelling, difficulty breathing, or generalized urticaria requiring immediate medical attention. Both pharmaceutical agents, such as doxycycline and therapeutic psoralens, and naturally occurring plant compounds including furocoumarins found in giant hogweed ( Heracleum mantegazzianum ), celery, parsley, and citrus fruits can induce phototoxic injury. Although the clinical appearance may resemble severe sunburn, the underlying mechanisms differ. Doxycycline primarily causes reactive oxygen species (ROS)-mediated oxidative injury, whereas furocoumarins undergo UV-A activation and form covalent DNA adducts, resulting in more profound and often longer-lasting cellular damage. The clinic...
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