The growth and maturation of ovum in mammals is caused by?

SJH Nursing Officer - 2019

Applied Physiology

Medium

Appeared in: SJH Nursing Officer - 2019

Explanation

The growth and maturation of the ovum is a multi-stage process requiring the coordinated action of two key hormones.
Follicle-Stimulating Hormone (FSH) is responsible for the initial recruitment and growth of ovarian follicles.
Luteinizing Hormone (LH) works with FSH to promote further development and is critically responsible for the final maturation of the ovum and triggering ovulation.
The early growth phase is mainly stimulated by FSH, but the greatly accelerated final growth and maturation require both FSH and LH.
A surge in LH is the direct trigger for ovulation, the release of the mature ovum. Without LH, the follicle will not progress to the stage of ovulation, even if FSH levels are high.

Option A: While FSH is essential for initiating follicular growth, it is not sufficient on its own to cause the final maturation and ovulation of the ovum. LH is required for these later-stage events.
Option B: LTH, or Luteotropic hormone, is another name for prolactin. Its primary role is stimulating milk production (lactation) after childbirth, not ovum maturation.
Option D: While LH is crucial for the final maturation and ovulation, it cannot act alone. It requires the initial follicular development that is stimulated by FSH.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of the ovarian cycle as background academic context rather than a clinical decision trigger.
Understanding the roles of FSH and LH is fundamental to managing infertility. Many treatments involve administering gonadotropins (like FSH and LH) to stimulate follicle development and induce ovulation in women who do not ovulate regularly.
Hormonal contraceptives (birth control pills) work by manipulating the levels of estrogen and progestin to suppress the pituitary's release of FSH and LH, thereby preventing follicular development and ovulation.
What if? If a patient has a condition causing high FSH but very low LH (e.g., certain types of hypogonadotropic hypogonadism), they would be able to start follicular growth but would fail to ovulate. Treatment would require supplementation with an LH-like activity (like hCG or recombinant LH) to complete the maturation process.

How to Approach the Question

First, identify the key processes in the question: 'growth' and 'maturation' of the ovum.
Recognize that these are distinct but connected phases of the ovarian cycle.
Recall the primary functions of the major reproductive hormones listed in the options: FSH, LH, and LTH (prolactin).
Analyze the role of each hormone: FSH is for 'Follicle-Stimulating,' so it starts the growth. LH has a 'Luteinizing' role and also triggers ovulation.
Evaluate if one hormone is sufficient for the entire process. Since growth is initiated by FSH and final maturation/ovulation is triggered by LH, conclude that both are necessary for the complete process.
Eliminate LTH as its primary function is lactation, not ovulation.

Concept Tested & Keywords

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E6 Physiology Guyton 4SAE Part 3 pp. 35-37, 33-35

E6 Pharmacology Katzung 16e p. 1049-1051