Question

Metestrus period is characterized by

• A. Increase in levels of both estrogen and LH
• B. Increase in level of estrogen and fall in level of LH
• C. Fall in levels of both estrogen and LH
• D. Fall in level of estrogen and increase in level of LH

Hint:

Estrous Cycle Hormones by Stage:
Proestrus = Estrogen rising.
Estrus = Peak Estrogen + LH Surge.
Metestrus = FALL in BOTH Estrogen and LH (Early CL forming).
Diestrus = Peak Progesterone.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Endocrinology of the bovine estrous cycle phases: metestrus (days 1--4) follows ovulation and is characterized by the postovulatory collapse of estrogen and baseline LH prior to peak luteal progesterone synthesis.
Key Formula or Approach:
\[ \text{Metestrus (Days 1--4): } \text{Estrogen} \downarrow \text{ (Follicle ruptured)} \quad \& \quad \text{LH} \downarrow \text{ (Basal post-surge levels)} \longrightarrow \text{Progesterone} \uparrow \]

Step 2: Detailed Explanation:
Hormonal dynamics across the four phases of the bovine estrous cycle:
1. Estrus (Day 0): Peak Estrogen surge and preovulatory LH surge trigger standing heat and ovulation.
2. Metestrus (Days 1 to 4): The period immediately following ovulation and rupture of the Graafian follicle:
- With the mature follicle gone, circulating Estrogen levels plunge precipitously.
- The preovulatory LH surge has completely subsided, so LH levels fall back to low basal baseline levels.
- Early luteinization of granulosa/theca cells begins in the corpus hemorrhagicum to initiate early progesterone production.
- Therefore, Metestrus is endocrine-characterized by a Fall in levels of both estrogen and LH.

Step 3: Final Answer:
Therefore, Metestrus is characterized by a Fall in levels of both estrogen and LH, corresponding to option (C).