What are the effects of progesterone injections (Progesterone, a steroid hormone)?

From the FDA Drug Label

ADVERSE REACTIONS: Breakthrough bleeding; spotting; change in menstrual flow; amenorrhea; edema; change in weight (increase or decrease); changes in cervical erosion and cervical secretions; cholestatic jaundice; breast tenderness and galactorrhea; pain, irritation, and/or redness at the injection area; skin sensitivity reactions consisting of urticaria, pruritus, edema and generalized rash; acne, alopecia and hirsutism; rash (allergic) with and without pruritus; anaphylactoid reactions; mental depression; pyrexia; insomnia; nausea; and somnolence. The effects of progesterone injections include:

• Hormonal effects: changes in menstrual flow, amenorrhea, breakthrough bleeding, spotting
• Local reactions: pain, irritation, and/or redness at the injection area
• Systemic effects: edema, change in weight, breast tenderness, galactorrhea, mental depression, pyrexia, insomnia, nausea, somnolence
• Dermatological effects: acne, alopecia, hirsutism, rash, urticaria, pruritus
• Other effects: cholestatic jaundice, anaphylactoid reactions 1

From the Research

Effects of Progesterone Injections

The effects of progesterone injections are varied and depend on the context of their use. Some of the key effects include:

• Preparation of the endometrium for implantation and maintenance of the gestational sac in the uterus 2
• Modulation of the maternal immune system 2
• Treatment of patients undergoing assisted reproductive technology procedures as a luteal phase support 2
• Potential treatment of threatening or recurrent miscarriage, although newer trials have neglected this beneficial effect 2

Physiological and Pharmacological Actions

Progesterone has a wide range of effects in physiology and human medicine, including:

• Neuro- and immunoprotective activities 3
• Maintenance of pregnancy and prevention of preterm labor 3
• Treatment of various gynecological pathologies and lowering the negative effects of menopause 3
• Potential applications in other medical fields, such as neuroregeneration and repair of brain damage 4

Safety and Side Effects

The safety and side effects of progesterone injections have been extensively studied, with findings including:

• Synthetic progestins may produce significant side effects, such as fatigue, fluid retention, and lipid level alterations 5
• Natural progesterones may have milder adverse effects, depending on the route of administration 5
• Micronized natural progesterone appears to be a safe and effective alternative to synthetic and natural progesterone formulations, with better bioavailability and fewer side effects 5

Forms of Progesterone Preparations

Progesterone preparations come in various forms, including:

• Oral, vaginal, and micro delivery systems, which can increase bioavailability and compliance 6
• Different routes of administration, such as intramuscular, intravenous, intravaginal, intranasal, transdermal, and rectal 5